submilli_engine/stdlib/

capabilities.rs

//! Catalog of the semantic-security capabilities the stdlib host functions
//! gate via `check_security`. This is the single source of truth behind
//! `submilli blueprint init`, the `submilli blueprint capability` verbs, and
//! the server's `GET /v1/capabilities`, so an operator sees every capability
//! the runtime can gate.
//!
//! **Keep in sync with the host functions.** When a host fn in `stdlib::fs` /
//! `stdlib::http` (or a new gated module) starts or stops gating a capability,
//! update the matching entry here — see AGENTS.md. The `capabilities` test in
//! the `submilli` CLI asserts every `example_filter` below parses.

use super::{OptionalPackage, Stdlib};

/// One context field a capability's `filter:` expression can match on.
pub struct FilterField {
    pub name: &'static str,
    /// The operand's shape in a filter comparison: `string`, `number`, or
    /// `boolean`.
    pub ty: &'static str,
    /// One line on what the field carries.
    pub doc: &'static str,
    /// How the runtime rewrites the value before the policy sees it.
    pub normalization: FieldNormalization,
}

/// A rewrite the runtime applies to a field's value before checking it. Call-site
/// derivation applies the same rewrite to a literal argument, so the filter it
/// writes into `requires` names the value the policy is asked about.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum FieldNormalization {
    /// Checked exactly as the caller passed it.
    Verbatim,
    /// Absolute guest path with `.` and `..` collapsed, as VFS I/O resolves it.
    VfsPath,
    /// The serialized form of the parsed HTTPS repository URL: lowercase host,
    /// no default port, `/` for an empty path, percent-encoded.
    RepositoryUrl,
}

impl FieldNormalization {
    /// The value the runtime checks for `value`, or why the runtime refuses it.
    pub(crate) fn apply(self, value: &str) -> Result<String, String> {
        match self {
            Self::Verbatim => Ok(value.to_string()),
            Self::VfsPath => {
                crate::runtime::fs::guest_normalize("/", value).map_err(|error| error.to_string())
            }
            Self::RepositoryUrl => {
                crate::stdlib::git::canonical_url(value).map_err(|error| error.to_string())
            }
        }
    }
}

const fn field(name: &'static str, ty: &'static str, doc: &'static str) -> FilterField {
    FilterField {
        name,
        ty,
        doc,
        normalization: FieldNormalization::Verbatim,
    }
}

const fn vfs_path_field(name: &'static str, doc: &'static str) -> FilterField {
    normalized_string_field(name, doc, FieldNormalization::VfsPath)
}

const fn normalized_string_field(
    name: &'static str,
    doc: &'static str,
    normalization: FieldNormalization,
) -> FilterField {
    FilterField {
        name,
        ty: "string",
        doc,
        normalization,
    }
}

/// One gated capability and the policy `filter:` surface it exposes.
pub struct Capability {
    /// The name passed to `check()` — exactly what a policy rule's
    /// `capability:` must equal (capability names are matched verbatim).
    pub name: &'static str,
    /// Why the runtime refuses this capability to `main` outright, ahead of the
    /// policy engine — `None` for an ordinary capability a rule can grant to any
    /// caller. A rule granting a marked capability to `main` is dead, so the
    /// surfaces that scaffold, add, and lint rules read this one fact rather
    /// than each restating the carve-out, and each shows the reason verbatim.
    pub main_denial: Option<&'static str>,
    /// One-line description of what gating the capability controls.
    pub summary: &'static str,
    /// Context fields a `filter:` expression can match on, as supplied by a
    /// representative call. Documents what a rule can constrain.
    pub filter_fields: &'static [FilterField],
    /// A ready-to-uncomment example `filter:` expression for the scaffold.
    pub example_filter: &'static str,
}

impl Capability {
    /// Whether the name is a template (`mcp.<server>`) rather than a concrete
    /// name a policy rule can use verbatim.
    pub fn is_template(&self) -> bool {
        self.name.contains('<')
    }

    /// Whether a policy rule granting this capability to `main` can take effect.
    pub fn grantable_to_main(&self) -> bool {
        self.main_denial.is_none()
    }

    /// The filter fields' names, for surfaces that don't show types.
    pub fn field_names(&self) -> impl Iterator<Item = &'static str> {
        self.filter_fields.iter().map(|f| f.name)
    }
}

/// A group of capabilities sharing a source module, for scaffold sectioning.
pub struct CapabilityGroup {
    /// The owning stdlib module, e.g. `submilli:fs`.
    pub module: &'static str,
    pub capabilities: &'static [Capability],
}

const PATH: FilterField = vfs_path_field("path", "Normalized absolute VFS path the call targets");
const RECURSIVE: FilterField = field(
    "recursive",
    "boolean",
    "Whether the operation applies recursively",
);
const FROM: FilterField = vfs_path_field("from", "Normalized absolute source VFS path");
const TO: FilterField = vfs_path_field("to", "Normalized absolute destination VFS path");
/// The code module checks workspace access as recursive.
const CODE_RECURSIVE: FilterField = field(
    "recursive",
    "boolean",
    "Always true; supplied by the code module only",
);
const KEY: FilterField = field("key", "string", "Session key the call targets");
const PREFIX: FilterField = field("prefix", "string", "Session key prefix being listed");

const FS: &[Capability] = &[
    Capability {
        name: "fs.read",
        main_denial: None,
        summary: "Read files and code workspace content (including search and ignore rules)",
        filter_fields: &[
            PATH,
            field(
                "length",
                "number",
                "Bytes requested; supplied by `readBytes` only",
            ),
            field(
                "chunkSize",
                "number",
                "Chunk size in bytes; supplied by `bytes` only",
            ),
            CODE_RECURSIVE,
        ],
        example_filter: "path glob \"*.csv\"",
    },
    Capability {
        name: "fs.write",
        main_denial: None,
        summary: "Create, write, append, or apply code edits to files",
        filter_fields: &[
            PATH,
            field(
                "length",
                "number",
                "Content size in bytes; supplied by `write`, `writeText`, `append`, \
                 `appendText`, and code edits",
            ),
            field(
                "max_bytes",
                "number",
                "Requested download size cap in bytes; supplied by `http.download` and packages that stream downloads",
            ),
            field(
                "diff",
                "string",
                "Unified diff of the edit; supplied by code edits only",
            ),
        ],
        example_filter: "path glob \"/out/*\"",
    },
    Capability {
        name: "fs.stat",
        main_denial: None,
        summary: "Inspect metadata (including code workspace discovery)",
        filter_fields: &[PATH, CODE_RECURSIVE],
        example_filter: "path glob \"/data/*\"",
    },
    Capability {
        name: "fs.list",
        main_denial: None,
        summary: "List directory entries (including code search, glob and tree)",
        filter_fields: &[PATH, RECURSIVE],
        example_filter: "path glob \"/data/*\"",
    },
    Capability {
        name: "fs.mkdir",
        main_denial: None,
        summary: "Create directories",
        filter_fields: &[PATH, RECURSIVE],
        example_filter: "path glob \"/tmp/*\"",
    },
    Capability {
        name: "fs.remove",
        main_denial: None,
        summary: "Delete files or directories",
        filter_fields: &[PATH, RECURSIVE],
        example_filter: "path glob \"/tmp/*\"",
    },
    Capability {
        name: "fs.move",
        main_denial: None,
        summary: "Move or rename a path",
        filter_fields: &[FROM, TO],
        example_filter: "to glob \"/archive/*\"",
    },
    Capability {
        name: "fs.copy",
        main_denial: None,
        summary: "Copy a path",
        filter_fields: &[FROM, TO, RECURSIVE],
        example_filter: "to glob \"/backup/*\"",
    },
];

const BRANCH: FilterField = field("branch", "string", "Local or requested remote branch name");
const REMOTE: FilterField = normalized_string_field(
    "remote",
    "Canonical HTTPS repository URL",
    FieldNormalization::RepositoryUrl,
);
const REMOTE_NAME: FilterField = field("remoteName", "string", "Named remote, for example origin");
const GIT: &[Capability] = &[
    Capability {
        name: "git.init",
        main_denial: None,
        summary: "Create a local repository and its VFS directory",
        filter_fields: &[PATH],
        example_filter: "path == \"/repo\"",
    },
    Capability {
        name: "git.clone",
        main_denial: None,
        summary: "Clone an HTTPS repository into a VFS directory",
        filter_fields: &[PATH, REMOTE_NAME, REMOTE, BRANCH],
        example_filter: "path == \"/repo\" and remote == \"https://github.com/acme/project.git\"",
    },
    Capability {
        name: "git.fetch",
        main_denial: None,
        summary: "Fetch or pull HTTPS remote branches into an existing repository",
        filter_fields: &[PATH, REMOTE_NAME, REMOTE, BRANCH],
        example_filter: "path == \"/repo\" and remote == \"https://github.com/acme/project.git\"",
    },
    Capability {
        name: "git.commit",
        main_denial: None,
        summary: "Commit staged changes with Blueprint identity",
        filter_fields: &[PATH, BRANCH],
        example_filter: "path == \"/repo\" and branch == \"main\"",
    },
];

const HTTP_VERB_FIELDS: &[FilterField] = &[
    field("host", "string", "Destination host, without port"),
    field("path", "string", "URL path component"),
    field("body_size", "number", "Request body size in bytes"),
    field("timeout_ms", "number", "Request timeout in milliseconds"),
];

const HTTP: &[Capability] = &[
    Capability {
        name: "http.get",
        main_denial: None,
        summary: "HTTP GET",
        filter_fields: HTTP_VERB_FIELDS,
        example_filter: "host == \"api.example.com\"",
    },
    Capability {
        name: "http.post",
        main_denial: None,
        summary: "HTTP POST",
        filter_fields: HTTP_VERB_FIELDS,
        example_filter: "host == \"api.example.com\"",
    },
    Capability {
        name: "http.put",
        main_denial: None,
        summary: "HTTP PUT",
        filter_fields: HTTP_VERB_FIELDS,
        example_filter: "host == \"api.example.com\"",
    },
    Capability {
        name: "http.patch",
        main_denial: None,
        summary: "HTTP PATCH",
        filter_fields: HTTP_VERB_FIELDS,
        example_filter: "host == \"api.example.com\"",
    },
    Capability {
        name: "http.delete",
        main_denial: None,
        summary: "HTTP DELETE",
        filter_fields: HTTP_VERB_FIELDS,
        example_filter: "host == \"api.example.com\"",
    },
    Capability {
        name: "http.head",
        main_denial: None,
        summary: "HTTP HEAD",
        filter_fields: HTTP_VERB_FIELDS,
        example_filter: "host == \"api.example.com\"",
    },
    Capability {
        name: "http.options",
        main_denial: None,
        summary: "HTTP OPTIONS",
        filter_fields: HTTP_VERB_FIELDS,
        example_filter: "host == \"api.example.com\"",
    },
    Capability {
        name: "http.download",
        main_denial: None,
        summary: "Download a URL straight to the VFS",
        filter_fields: &[
            field("host", "string", "Download host, without port"),
            field("url_path", "string", "URL path component"),
            vfs_path_field(
                "vfs_path",
                "Normalized absolute destination path in the VFS",
            ),
            field(
                "max_bytes",
                "number",
                "Requested download size cap in bytes",
            ),
            field(
                "overwrite",
                "boolean",
                "Whether an existing file may be clobbered",
            ),
            field(
                "decompress",
                "boolean",
                "Whether the response is decompressed on write",
            ),
        ],
        example_filter: "host == \"cdn.example.com\" and overwrite == false",
    },
];

/// Every other method `http.request` takes, gated as `http.<method>` with the
/// method lowercased: `http.request("TRACE", …)` checks `http.trace`. Kept
/// out of [`CORE_CATALOG`], whose consumers read a templated name as
/// `mcp.<server>` and concretize it per declared server; see
/// [`uncataloged_http_method`].
pub const HTTP_OTHER_METHOD: Capability = Capability {
    name: "http.<method>",
    main_denial: None,
    summary: "Any other HTTP method, through `http.request`: `http.trace` gates TRACE",
    filter_fields: HTTP_VERB_FIELDS,
    example_filter: "host == \"api.example.com\"",
};

/// Outbound MCP calls — one capability per declared server, `mcp.<server>` (the
/// `<server>` placeholder is filled in per blueprint, whose `mcp:` block names its
/// servers). The tool being called is in the filter context, so a rule can allow a
/// server broadly or constrain it to specific tools.
const MCP: &[Capability] = &[Capability {
    name: "mcp.<server>",
    main_denial: None,
    summary: "Call tools on a declared outbound MCP server (streamable_http)",
    filter_fields: &[
        field("tool", "string", "Name of the MCP tool being called"),
        field(
            "transport",
            "string",
            "MCP transport; always \"streamable_http\" today",
        ),
    ],
    example_filter: "tool == \"create_issue\"",
}];

const EMBEDDING: &[Capability] = &[Capability {
    name: "embedding.embed",
    // No `main_denial`: main-module access is the point. The program names an
    // alias and supplies text; the credential is resolved inside the provider
    // and never returned.
    main_denial: None,
    summary: "Embed text through a declared embedding alias (embed) and enumerate the aliases \
              it may use (models). Narrowing `model` also narrows what `models()` reveals: \
              every candidate is filtered through this same rule, so a listing never offers \
              an alias the caller would be denied at call time. A policy allowing no \
              candidates returns an empty listing",
    filter_fields: &[
        field(
            "model",
            "string",
            "Alias the call targets or the candidate being listed. The runtime preflight \
             does not ask policy about an empty name",
        ),
        field(
            "input_count",
            "number",
            "Texts in this call — N for embed, 0 for models. Input text is never in this \
             context",
        ),
    ],
    example_filter: "model glob \"memory-*\"",
}];

const LLM: &[Capability] = &[Capability {
    name: "llm.call",
    // No `main_denial`: main-module access is the point. A model call is not a
    // secret read — the program names a model and supplies a prompt, and the
    // credential is resolved inside the provider and never returned.
    main_denial: None,
    summary: "Call a model (call, batch) and enumerate the models it may call (models). \
              Narrowing `model` also narrows what `models()` reveals: every candidate is \
              filtered through this same rule, so a listing never offers a model the \
              caller would be denied at call time. A policy allowing no candidates \
              returns an empty listing",
    filter_fields: &[
        field(
            "model",
            "string",
            "Model name the call targets or the candidate being listed. \
             The runtime preflight does not ask policy about an empty name",
        ),
        field(
            "prompt_count",
            "number",
            "Prompts in this dispatch — 1 for call, N for batch, 0 for models. Prompt text \
             is never in this context",
        ),
    ],
    example_filter: "model glob \"claude-*\"",
}];

const SECRETS: &[Capability] = &[Capability {
    name: "secrets.get",
    main_denial: Some(
        "secret values are never available to main-module code, and no policy can \
         grant this. The package that needs this credential resolves it internally \
         and never returns it — pass the secret NAME to that package's API instead",
    ),
    summary: "Read a Blueprint-declared secret value",
    filter_fields: &[field("name", "string", "Declared secret name being read")],
    example_filter: "name == \"STRIPE_API_KEY\"",
}];

const SESSION: &[Capability] = &[
    Capability {
        name: "session.read",
        main_denial: None,
        summary: "Read session state (get, has), and decide which keys a list may reveal",
        filter_fields: &[KEY],
        example_filter: "key glob \"triage/*\"",
    },
    Capability {
        name: "session.write",
        main_denial: None,
        summary: "Store or overwrite a session value (set)",
        filter_fields: &[KEY],
        example_filter: "key glob \"triage/*\"",
    },
    Capability {
        name: "session.remove",
        main_denial: None,
        summary: "Delete a session key",
        filter_fields: &[KEY],
        example_filter: "key glob \"triage/*\"",
    },
    Capability {
        name: "session.list",
        main_denial: None,
        summary: "Enumerate session keys under a prefix",
        filter_fields: &[PREFIX],
        example_filter: "prefix == \"triage/\"",
    },
];

/// The capabilities of the core packages, which every embedder has.
const CORE_CATALOG: &[CapabilityGroup] = &[
    CapabilityGroup {
        module: "submilli:embedding",
        capabilities: EMBEDDING,
    },
    CapabilityGroup {
        module: "submilli:fs",
        capabilities: FS,
    },
    CapabilityGroup {
        module: "submilli:git",
        capabilities: GIT,
    },
    CapabilityGroup {
        module: "submilli:http",
        capabilities: HTTP,
    },
    CapabilityGroup {
        module: "submilli:llm",
        capabilities: LLM,
    },
    CapabilityGroup {
        module: "@mcp",
        capabilities: MCP,
    },
    CapabilityGroup {
        module: "submilli:secrets",
        capabilities: SECRETS,
    },
    CapabilityGroup {
        module: "submilli:session",
        capabilities: SESSION,
    },
];

const AGENT: FilterField = field(
    "agent",
    "string",
    "The sub-agent's name, as `submilli:agents` list() names it",
);

const AGENTS: CapabilityGroup = CapabilityGroup {
    module: "submilli:agents",
    capabilities: &[Capability {
        name: "agent.run",
        main_denial: None,
        summary: "Hand work to a harness sub-agent, or list the agents",
        filter_fields: &[AGENT],
        example_filter: "agent == \"researcher\"",
    }],
};

const SKILL: FilterField = field(
    "name",
    "string",
    "The skill's name, as `submilli:skills` list() names it",
);

const SKILLS: CapabilityGroup = CapabilityGroup {
    module: "submilli:skills",
    capabilities: &[Capability {
        name: "skill.load",
        main_denial: None,
        summary: "Load a harness skill, read its files, or list the skills",
        filter_fields: &[SKILL],
        example_filter: "name == \"code-review\"",
    }],
};

/// The capabilities of one optional package.
fn optional_group(package: OptionalPackage) -> &'static CapabilityGroup {
    match package {
        OptionalPackage::Agents => &AGENTS,
        OptionalPackage::Skills => &SKILLS,
    }
}

/// Every capability the core packages gate, grouped by source module. An
/// optional package's capabilities are listed only by [`catalog_for`].
pub fn catalog() -> &'static [CapabilityGroup] {
    CORE_CATALOG
}

/// Every capability the packages of `stdlib` gate, grouped by source module,
/// in [`catalog`]'s order: by module name without its `submilli:` or `@` prefix.
pub fn catalog_for(stdlib: Stdlib) -> Vec<&'static CapabilityGroup> {
    let mut groups: Vec<&'static CapabilityGroup> = CORE_CATALOG.iter().collect();
    groups.extend(stdlib.optional_packages().map(optional_group));
    groups.sort_by_key(|group| catalog_order(group.module));
    groups
}

fn catalog_order(module: &str) -> &str {
    module
        .strip_prefix("submilli:")
        .or_else(|| module.strip_prefix('@'))
        .unwrap_or(module)
}

/// Every group the runtime can gate, whichever packages an embedder enables.
/// Runtime checks use this: a capability reaches them only from a host
/// function, which is installed only when its package is enabled.
pub(crate) fn all_groups() -> impl Iterator<Item = &'static CapabilityGroup> {
    CORE_CATALOG.iter().chain(
        OptionalPackage::ALL
            .iter()
            .map(|package| optional_group(*package)),
    )
}

/// Look up a core capability by its exact name (templates included, by their
/// literal `mcp.<server>` spelling).
pub fn find(name: &str) -> Option<&'static Capability> {
    find_for(Stdlib::core(), name)
}

/// [`find`] among the capabilities of `stdlib`.
pub fn find_for(stdlib: Stdlib, name: &str) -> Option<&'static Capability> {
    catalog_for(stdlib)
        .into_iter()
        .flat_map(|group| group.capabilities)
        .find(|cap| cap.name == name)
}

/// [`find`] among every group the runtime can gate.
pub(crate) fn find_any(name: &str) -> Option<&'static Capability> {
    all_groups()
        .flat_map(|group| group.capabilities)
        .find(|cap| cap.name == name)
}

/// The method of a name that fills [`HTTP_OTHER_METHOD`]: `http.` and a method
/// token in the lowercase form the runtime checks, which the catalog has no
/// entry for.
pub fn uncataloged_http_method(name: &str) -> Option<&str> {
    let method = name.strip_prefix("http.")?;
    (is_lowercase_http_token(method) && find(name).is_none()).then_some(method)
}

/// The entry describing `name`: its catalog entry, or [`HTTP_OTHER_METHOD`]
/// for a name that fills it.
pub fn find_gating(name: &str) -> Option<&'static Capability> {
    find_gating_for(Stdlib::core(), name)
}

/// [`find_gating`] among the capabilities of `stdlib`.
pub fn find_gating_for(stdlib: Stdlib, name: &str) -> Option<&'static Capability> {
    find_for(stdlib, name).or_else(|| uncataloged_http_method(name).map(|_| &HTTP_OTHER_METHOD))
}

/// An RFC 9110 method token, the set `http.request` accepts, in lowercase.
fn is_lowercase_http_token(method: &str) -> bool {
    !method.is_empty()
        && method.bytes().all(|byte| {
            byte.is_ascii_lowercase() || byte.is_ascii_digit() || b"!#$%&'*+-.^_`|~".contains(&byte)
        })
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::collections::HashSet;

    /// Marking a capability not-grantable-to-`main` changes the runtime's
    /// answer for every caller, so growing the set is a deliberate act.
    #[test]
    fn only_secrets_get_is_refused_to_main() {
        let refused: Vec<&str> = all_groups()
            .flat_map(|group| group.capabilities)
            .filter(|cap| !cap.grantable_to_main())
            .map(|cap| cap.name)
            .collect();
        assert_eq!(refused, ["secrets.get"]);
    }

    /// The core set lists exactly the core catalog, in the same order, so every
    /// surface that reads `catalog()` agrees with one that reads `catalog_for`.
    #[test]
    fn core_set_lists_the_core_catalog() {
        let core: Vec<&str> = catalog().iter().map(|group| group.module).collect();
        let for_core: Vec<&str> = catalog_for(Stdlib::core())
            .iter()
            .map(|group| group.module)
            .collect();
        assert_eq!(for_core, core);
    }

    #[test]
    fn catalog_entries_are_well_formed() {
        let mut seen = HashSet::new();
        for group in all_groups() {
            for cap in group.capabilities {
                assert!(
                    cap.name.contains('.') && !cap.name.is_empty(),
                    "capability name '{}' must be `module.action`",
                    cap.name
                );
                assert!(seen.insert(cap.name), "duplicate capability '{}'", cap.name);
                assert!(!cap.summary.is_empty(), "{}: empty summary", cap.name);
                // `filter_fields` may be empty for a capability gated by name alone
                // (e.g. the `@mcp` family, whose name already pins server + tool).
                assert!(
                    !cap.example_filter.is_empty(),
                    "{}: empty example_filter",
                    cap.name
                );
                assert!(
                    cap.main_denial.is_none_or(|reason| !reason.is_empty()),
                    "{}: empty main_denial reason",
                    cap.name
                );
                for f in cap.filter_fields {
                    assert!(!f.name.is_empty(), "{}: unnamed filter field", cap.name);
                    assert!(
                        matches!(f.ty, "string" | "number" | "boolean"),
                        "{}.{}: unknown field type '{}'",
                        cap.name,
                        f.name,
                        f.ty
                    );
                    assert!(!f.doc.is_empty(), "{}.{}: empty doc", cap.name, f.name);
                }
            }
        }
    }

    #[test]
    fn session_group_is_cataloged() {
        let group = catalog()
            .iter()
            .find(|g| g.module == "submilli:session")
            .expect("submilli:session group");
        let names: Vec<&str> = group.capabilities.iter().map(|cap| cap.name).collect();
        assert_eq!(
            names,
            [
                "session.read",
                "session.write",
                "session.remove",
                "session.list"
            ]
        );
        assert_eq!(
            find("session.list")
                .unwrap()
                .field_names()
                .collect::<Vec<_>>(),
            ["prefix"]
        );
    }

    #[test]
    fn embedding_group_is_cataloged() {
        let group = catalog()
            .iter()
            .find(|g| g.module == "submilli:embedding")
            .expect("submilli:embedding group");
        let names: Vec<&str> = group.capabilities.iter().map(|cap| cap.name).collect();
        assert_eq!(names, ["embedding.embed"]);
        let capability = find("embedding.embed").unwrap();
        assert_eq!(
            capability.field_names().collect::<Vec<_>>(),
            ["model", "input_count"]
        );
        assert_eq!(capability.example_filter, "model glob \"memory-*\"");
        assert!(capability.main_denial.is_none());
        assert!(
            capability.summary.contains("models()"),
            "the summary must say narrowing `model` narrows discovery: {}",
            capability.summary
        );
    }

    #[test]
    fn llm_group_is_cataloged() {
        let group = catalog()
            .iter()
            .find(|g| g.module == "submilli:llm")
            .expect("submilli:llm group");
        let names: Vec<&str> = group.capabilities.iter().map(|cap| cap.name).collect();
        assert_eq!(names, ["llm.call"]);
        assert_eq!(
            find("llm.call").unwrap().field_names().collect::<Vec<_>>(),
            ["model", "prompt_count"]
        );
        // The double gate lives in the summary wording and the host fn, not in
        // the struct, so an operator reading only the catalog still has to learn
        // that narrowing `model` also shortens what `models()` returns.
        let summary = find("llm.call").unwrap().summary;
        assert!(
            summary.contains("models()"),
            "the summary must say narrowing `model` narrows discovery: {summary}"
        );
    }

    #[test]
    fn uncataloged_http_methods_fill_the_template() {
        assert_eq!(uncataloged_http_method("http.trace"), Some("trace"));
        assert_eq!(uncataloged_http_method("http.propfind"), Some("propfind"));
        // Cataloged, the template itself, uppercase (the runtime lowercases),
        // empty, or not a token.
        for name in [
            "http.get",
            "http.<method>",
            "http.TRACE",
            "http.",
            "http.a b",
            "fs.trace",
        ] {
            assert!(uncataloged_http_method(name).is_none(), "{name}");
        }
        assert!(HTTP_OTHER_METHOD.is_template());
        assert_eq!(
            find_gating("http.trace").map(|c| c.name),
            Some("http.<method>")
        );
        assert_eq!(find_gating("http.get").map(|c| c.name), Some("http.get"));
    }

    #[test]
    fn find_and_is_template() {
        assert_eq!(find("fs.read").map(|c| c.name), Some("fs.read"));
        assert!(find("fs.nope").is_none());
        assert!(find("mcp.<server>").is_some_and(Capability::is_template));
        assert!(!find("fs.read").unwrap().is_template());
    }
}