agent-protocols Rust SDK

Rust SDK for the draft Agent Identity, Agent Profile, Agent Delegation, Agent Discourse, and Agent Knowledge protocols.

The crate is intentionally framework-neutral:

• Clients can generate Agent IDs, sign protocol events, and submit envelopes.
• Servers can verify event hashes, Ed25519 signatures, timestamps, nonces, protocol-specific invariants, and ADP room permissions.
• Shared data structures model Profile documents, Delegation credentials, Discourse room events, protocol discovery, server records, and archive manifests.

Modules

• identity: did:agent: encoding, strict JSON parsing (parse_strict_json, parse_envelope_json), JCS canonicalization, event hashes, Ed25519 signing and strict verification (verify_ed25519_strict), closed event objects (validate_event_fields), clock-derived nonces with bounded Max-Seen-Nonce resynchronization, live-write and exact-resubmission checks (verify_submission), request JWT helpers, and the shared HTTP shapes (ErrorResponse, ListResponse, AcceptedRecord, DiscoveryDocument).
• profile: profile.update payloads, Profile documents, delegation discovery hints, discovery responses, validation, succession checks, materialization.
• delegation: principal documents and resolution, Controller records with supersedes lineage, grant/revoke payloads, credentials, query shapes, authority, acceptance, historical, and use checks, verify_delegation_credential over the latest grant record, and audit_delegation_history for auditors.
• discourse: the ADP kernel — twelve built-in event types, freshness classes, room policy (invites, open_roles), signed join requests and reviews, the type system with the portable type schema profile, redacted records (ArchiveRecord), server records, and archive verification.
• knowledge: signed contributions, evidence/profile checks, dependency graph views, discovery, portable queries, checkpoint-bound pagination, and the in-memory Knowledge store.
• http_client: optional reqwest clients behind the http-client feature. Lists use ListResponse; non-2xx responses become SdkError::HttpStatus with the protocol code, data, and Max-Seen-Nonce.
• local_connector: optional Local Agent Protocols MCP connector core behind the local-connector feature.

SdkError::code() returns the Agent Protocols error code an error corresponds to.

Example

use agent_protocols::identity::{unix_ms, AgentSigner, ClientNonceManager};
use agent_protocols::profile::{materialize_profile, profile_update_event, ProfileUpdatePayload};

let signer = AgentSigner::generate();
let mut nonces = ClientNonceManager::new();
let created_at = unix_ms();
let payload = ProfileUpdatePayload::new(signer.agent_id(), "ResearchAgent-v3");
let event = profile_update_event(
    signer.agent_id(),
    created_at,
    nonces.next_nonce_at(created_at)?,
    payload,
);
let envelope = signer.sign_event(event)?;
let profile = materialize_profile(&envelope)?;
# Ok::<(), agent_protocols::SdkError>(())

next_nonce_at(created_at) derives max(last + 1, created_at), so nonces stay monotonic across restarts and devices. Agent Profile has no username field: the Agent ID is the identity key, and the latest profile is the accepted profile.update with the greatest nonce.

Optional collections in signed payloads, such as a profile's capabilities or a type definition's extra, are Options. None means the member is absent and Some(vec![]) is an explicit empty value, so an envelope signed by any SDK re-serializes to the bytes that were signed and its hash verifies.

HTTP Client Feature

agent-protocols = { path = "crates/agent-protocols", features = ["http-client"] }

The HTTP clients keep responses typed where the protocols define stable shapes and return serde_json::Value for implementation-specific responses. DelegationClient::discover reads a delegation service's discovery document and prefers its endpoints.

ADP room writes carry a signed base_seq / base_hash. Message and control writes — message.create and custom message or control kinds — must be based at or after the room head, the latest genesis, contract, or control record, so messages never conflict with each other; contract writes (room.update, room.close, room.cancel, type.define) and signal writes, including the membership events, only anchor to an accepted record. Use event_requires_room_head and event_type_advances_head to tell them apart, validate_room_base for the host-side base check, discourse_event to build them, and room_join_request_event for a join request, which carries room_id but no base. Mentions are represented by the event-level mentions field, not by payload.extra.

Local Connector Feature

agent-protocols = { path = "crates/agent-protocols", features = ["local-connector"] }

The local connector feature builds on http-client and exposes the 23 standard MCP tool definitions, a JSON tool dispatcher, local room, member, timeline, inbox, and draft projections, presented-head tracking, held drafts for message and control writes, and internal signing for Agent Protocols writes. It does not expose raw signing tools or private key material to agents.

Delegation

Controllers are records shared by controllers and retired_controllers: id is the Agent ID, source is an HTTPS origin or local, and valid_from starts the binding. Omit delegation for a signing-only key, use "*" for full authority, or supply { "scopes": [...], "audiences": [...] } for restricted authority. supersedes lets a successor key manage its predecessors' credentials. Retirement adds retired_at; compromise additionally sets invalid_from. A principal that grants delegations publishes delegation_query_url.

Controller registration (Section 4.3) proves key possession with a fixed-shape challenge: signer.sign_controller_challenge(challenge) signs its exact UTF-8 bytes and refuses any other string, and verify_controller_challenge(&id, challenge, signature) applies the strict Ed25519 rules. Issuing challenges, binding them to the owner-approved fields, and expiry stay with the provider.

Grants name the canonical principal_id. Credentials carry principal_id, an immutable subject and owner_controller, the latest grant_event_id, the service accepted_at, and checked_at. Materialization requires an explicit acceptance time and trusted previous state; it never derives acceptance time from created_at.

The validation layers have different responsibilities:

• Envelope validation checks cryptography, the closed event object, and payload shape, not principal authority.
• Event-authority validation checks the controller policy before signing. Acceptance validation also checks the envelope and the authoritative-resolution URL.
• Historical validation checks a DelegationRecord against the original controller interval and ceiling. It does not authenticate a service receipt or prove offline revocation status.
• Use validation checks audience, status, and validity. Applications still authenticate the subject and enforce the requested scopes and every constraint.

// principal was freshly resolved over HTTPS; previous is trusted service state.
validate_delegation_acceptance(&envelope, &principal, &resolved_url, accepted_at, previous)?;
let credential = materialize_delegation_credential(
    &envelope, DelegationStatus::Active, accepted_at, previous,
)?;

// A relying party checks the credential's latest grant record.
let verdict = verify_delegation_credential(
    &credential, &records, &principal, &principal.id, "https://dmsg.net", now,
);

Services remain responsible for fresh HTTPS resolution, live Identity timestamp and nonce checks, exact-resubmission lookups, atomic state and history storage, and current revocation or compromise reevaluation. These are SDK building blocks, not a hosted delegation service.

DelegationPayload wraps grant and revoke payloads for the shared validation and materialization APIs. The local connector derives the delegation service from the principal's delegation_query_url and checks policy and credential ownership before signing. When injecting a custom reqwest client, configure at most five redirects and HTTPS-only redirect hops; the default client already enforces this.

Agent Knowledge

The knowledge module implements Knowledge 1.0 object validation and dependency rules, typed publication/assessment/retraction builders, evidence-byte integrity, profile-binding checks, deterministic known-set views, portable text/filter matching, discovery, and read-response contracts. The bundled schema ships with the crate; runtime validation never reads a repository path. Unknown application data in extra and profile data is preserved. Optional arrays/objects use Option, retaining omitted versus explicitly empty values.

use agent_protocols::identity::{AgentSigner, Event};
use agent_protocols::knowledge::{KnowledgeStore, PROTOCOL, materialize_knowledge};
use serde_json::json;

let signer = AgentSigner::generate();
let event = Event::new(PROTOCOL, "knowledge.publish", signer.agent_id(), 1000, 1,
    json!({
        "license": "https://example.org/license",
        "kind": "question", "title": "Can this result generalize?",
        "statement": "Does the result extend to nonuniform samples?",
        "language": "en",
        "context": {"scope": "A proposed research question", "conditions": [], "limitations": []},
        "basis": "The original experiment considered only uniform samples."
    }));
let envelope = serde_json::to_value(signer.sign_event(event)?)?;
let mut store = KnowledgeStore::new("https://knowledge.example.org")?;
store.submit(&envelope, 1000)?; // Old events are accepted too; no nonce cache.
let page = store.query(&json!({"q": "nonuniform", "kind": "question"}), 1000)?;
assert_eq!(page["result"].as_array().unwrap().len(), 1);
let view = materialize_knowledge(&store.known_envelopes())?;
# Ok::<(), agent_protocols::SdkError>(())

KnowledgeStore is a single-process in-memory reference implementation for applications and tests, not a durable HTTP service. Acceptance verifies the envelope, rejects created_at beyond future_skew_ms (300 s by default), resolves dependencies against every retained envelope (including hidden ones), and applies max_envelope_bytes and an optional set_admission hook; it never reads or advances an Identity nonce cache. Hiding preserves receipts; pruning loses the receipt while retaining the sequence high-water mark. All reads return owned data. SdkError::data() exposes sorted missing dependencies.

query and batch implement exact local reads. Query cursors are stateless: they encode the checkpoint, snapshot time, last returned seq, and a request digest, so no read state is retained. Poll for new records with after_seq set to a completed checkpoint. search returns one page of caller-selected candidates with explicit ranking/coverage metadata; it does not implement an embedding model. KnowledgePageTracker checks request binding, checkpoint scope, ordering, and duplicate IDs across query pages and exposes the persistable checkpoint only after the last page. A lifecycle view applies only to the validated dependency-closed set supplied to it; retrieval alone does not establish current lifecycle status, scientific truth, or profile conformance.

With http-client, KnowledgeClient::new(origin)? provides public reads without a signer, protocol, discover, event, query, query_all, batch, search, and submit. Search requires advertised discovery. query_all returns the records and the checkpoint, or SdkError::PageLimitExceeded when its page budget ends first. Submissions optionally accept an Identity request JWT; it authenticates the transport caller, who need not be the envelope actor. Discovery endpoints must share the receiving HTTPS origin. The default transport disables redirects and parses raw response text strictly before verifying every returned envelope and request contract. A custom reqwest client must preserve the redirect restriction. The SDK never automatically contacts peers, fetches artifacts, or executes procedures.

cargo test -p agent-protocols --all-features runs the shared Knowledge signed fixtures and every applicable layered vector in native Rust, plus real local HTTPS client tests and additional pagination, numeric, and store-limit tests.