Struct ToolSchema 

#[non_exhaustive]
pub struct ToolSchema {
    pub name: String,
    pub description: String,
    pub params: Vec<ParamSchema>,
    pub examples: Vec<Example>,
    pub map_positionals: bool,
    pub subcommands: Vec<ToolSchema>,
    pub aliases: Vec<String>,
    pub owns_output: bool,
}

Schema describing a tool’s interface.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

name: String

Tool name.

description: String

Short description.

params: Vec<ParamSchema>

Parameter definitions.

examples: Vec<Example>

Usage examples.

map_positionals: bool

Map remaining positional args to named params by schema order. Only for MCP/external tools that expect named JSON params. Builtins handle their own positionals and should leave this false.

subcommands: Vec<ToolSchema>

Child schemas for subcommand-aware tools (kj context list, …).

Empty for flat tools (cat, grep, ls) — they take the flat binding path. When non-empty, the kernel walks leading positionals to pick the active leaf and binds flags against that leaf’s params (see select_leaf in the kernel).

skip_serializing_if keeps the wire compact for the many flat tools (no "subcommands":[] noise); default is then required so a flat tool’s payload (key absent) deserializes back to empty.

aliases: Vec<String>

Command-level aliases (ls → list, rm → remove), matched when routing a positional to a child. Distinct from ParamSchema::aliases, which name flags.

owns_output: bool

The tool renders its own output, including --json — the kernel must not re-format its ExecResult through apply_output_format.

Default false: a tool returns typed crate::OutputData and the kernel renders the requested format uniformly. Set true for tools with bespoke JSON envelopes (e.g. an embedder’s kj): they consume --json themselves and emit final bytes. See ToolSchema::with_owned_output.

Implementations

impl ToolSchema

pub fn new( name: impl Into<String>, description: impl Into<String>, ) -> ToolSchema

Create a new tool schema.

pub fn with_positional_mapping(self) -> ToolSchema

Enable positional->named parameter mapping for MCP/external tools.

pub fn param(self, param: ParamSchema) -> ToolSchema

Add a parameter to the schema.

pub fn example( self, description: impl Into<String>, code: impl Into<String>, ) -> ToolSchema

Add an example to the schema.

pub fn subcommand(self, child: ToolSchema) -> ToolSchema

Add a child schema, making this a subcommand-aware tool.

pub fn with_command_aliases( self, aliases: impl IntoIterator<Item = impl Into<String>>, ) -> ToolSchema

Set command-level aliases (e.g. ls for a list subcommand). These name the command, not its flags; flag aliases live on each ParamSchema.

pub fn matches_command(&self, word: &str) -> bool

True if word names this command — its name or any of its command-level aliases. Used when routing a positional to a child.

pub fn with_owned_output(self) -> ToolSchema

Declare that this tool renders its own output (including --json), so the kernel won’t re-format its result.

Applies to the whole tree: every subcommand is marked too, and a json param is advertised on each node that doesn’t already declare one. Reflection skips json as the kernel-global output flag, so this re-advertises it for tools that genuinely own it — closing the loop so help <tool> <sub> lists --json where the tool actually handles it.

Trait Implementations

impl Clone for ToolSchema

fn clone(&self) -> ToolSchema

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ToolSchema

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ToolSchema

fn deserialize<__D>( __deserializer: __D, ) -> Result<ToolSchema, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for ToolSchema

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.