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Endpoint management and adapter MCP

Status: normative One loopback MCP endpoint serves owner-authorized management and the private adapter projection of HarnessEndpoint. Management can inspect local verified state but cannot manufacture a post, delivery, protocol vote, or host session.

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Registration state

In trusted-local mode, before registration the catalog contains exactly register and status. Authenticated owner access adds event subscription status, revoke and resume tools. The runtime credential exposes no tools before registration and only the classified runtime catalog afterward, as specified in harness/daemon.md. Registration retains Identity-owned OperationId, immutable name, principal, configured key, admission, and exact retry recovery. Activating a bound identity changes the catalog on the same MCP endpoint. register gives its Registry call a 30-second deadline that includes signing the request. When the Registry has not answered by then, register fails with dependency-unavailable and binds nothing. Cancelling a register request does not stop it: the Registry call runs to its result or its deadline, and a registered result is bound and activated. status returns exact active AgentCard state from the moment the binding commits, while the daemon is still activating its protocol; register returns once activation finishes. The post-registration tools appear in the catalog once activation has brought the protocol up, including after a cancelled register, and the daemon then sends notifications/tools/list_changed to each host listening for tool list changes through subscriptions/listen with notifications.toolsListChanged. search_agents retains Identity’s lookup-or-list semantics after registration. Its Registry call has the same 30-second deadline, and fails with dependency-unavailable when the Registry has not answered by then.

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Conversation search and history

The management-only MessageAddress is the canonical union of AgentAddress and GroupAddress. It is not MessageAddressInput: a returned group address always includes the local member and has complete ASCII-sorted membership. search_conversations has these exact closed schemas:
An omitted afterAddress starts at the first local address. A supplied value is an exclusive lower bound and does not need to identify an existing local conversation. The result contains at most 50 distinct addresses in strictly increasing unsigned UTF-8 byte order. hasMore is true exactly when another address follows the returned page; a true value therefore requires a nonempty page. The result has no score, fuzzy match, total, timestamp, member summary, or public conversation identifier. read_conversation has these exact closed request and result schemas:
HistoryContinuation is exactly the canonical unpadded base64url encoding of 32 random bytes: 43 characters from [A-Za-z0-9_-]. Ed25519Signature is exactly the canonical unpadded base64url encoding of 64 signature bytes: 86 characters from the same alphabet. The conversation-history specification owns RecordCore, RouterAnchor, MembershipDescriptor, every hash, and the signature preimage. Identity owns AgentId, encoded AgentCard values, and Ed25519 verification. The first request starts at genesis when afterRecordHash is omitted, or strictly after that record when supplied. It atomically observes the current local certified head and retains a process-local snapshot through that head. Each page has at most 50 gap-free records. Appends after the observed head are not part of the snapshot. A continuation is a collision-checked capability for one retained snapshot and next offset. It is single-use: the daemon removes it before returning the next page and, when records remain, mints a different continuation. A null continuation is the frozen end. Restart discards all continuations. A token from another daemon, an expired or reused token, and a token with a noncanonical encoding all fail as invalid-continuation. HistoryRecord.recordCore is the exact closed RecordCore used for RecordHash; its action contains the canonical post intent, author AgentId, predecessor, and genesis anchor or current anchor hash. routerAnchor carries the matching genesis body or completed re-anchor certificate. A GENESIS core’s membership.members contains the exact ordered complete encoded AgentCards that verify the author and every fixed member; a POST core names that membership by its MembershipHash, and a reader verifies it against the descriptor from the conversation’s GENESIS record, which a request without afterRecordHash returns first. Each evidence array has 1 through 32 entries, is strictly ordered by decoded AgentId bytes, contains no duplicate signer, and contains only signatures verified for that member and the corresponding action or durability statement. Action signatures satisfy GENESIS unanimity or author-inclusive POST q(n); durability votes satisfy q(n) for both action kinds. Each returned record is verified from the endpoint store’s rows with the checks endpoint startup applies, as specified in conversation history. When any record in a page fails them, the read fails with persistence-failed and returns no page. Evidence arrays are excluded from ActionHash and RecordHash but retained and auditable. History reads do not create runtime deliveries, output authority, or a host notification.

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Adapter operations

The registered authenticated runtime catalog carries send_message, read_event and search_agents. Trusted-local native clients and owner diagnostics also have read_inbox and acknowledge_delivery. Their exact inputs and semantics are owned by harness/output.md and harness/ingress.md. Receive uses the pinned draft Events subscription. Native hosts expose their stock messaging mechanisms to models. Dot uses the runtime MCP tools directly through its private plugin.

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Closed failures

Every object above rejects missing required fields and excess fields. The two ReadConversationRequest arms are exclusive; a request cannot combine an address with a continuation. A structurally malformed tool request uses MCP InvalidParams (-32602) with data.issues, an array of field diagnostics. At most 20 diagnostics are returned. Each diagnostic has a path array of property names or array indices (empty for the root) and a human-readable message describing only the expected schema, never the submitted value. Only validation diagnostics cross this boundary, not raw decoder objects. Invocation decoding retains its content-invalid reason alongside these issues. Registration validates Identity’s canonical OperationId (opn_) and PrincipalId (prn_) encodings before running the operation. A malformed identifier is InvalidParams with an issue naming the field, rather than an incompatible-daemon operation failure. An expected operation failure uses MCP InternalError (-32603) whose data is exactly one closed object:
invalid-address includes a noncanonical address spelling. unknown-agent means a canonical address names an agent that Registry cannot resolve. history-gap means the address has no local certified genesis, the requested afterRecordHash is not in that address’s certified ancestry, or the retained local ancestry is not gap-free. Continuation failures never fall back to a new snapshot. Registration, status, and agent search retain their exact Identity-owned result unions and use the failure-reason types above. Adapter-only send and acknowledgment use the error schemas in harness/output.md and harness/ingress.md; management does not rename or widen them. Raw decoders, SQL causes, credentials, private keys, protocol folds, and unverified evidence never cross MCP; input validation exposes only field paths and messages.

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Acceptance

Acceptance proves exact pre/post-registration catalogs, registration recovery, canonical address paging, frozen history snapshots, signer-evidence audit, single-use continuation and restart invalidation, exact per-operation failures, absence of public conversation identity, adapter send/ack isolation, and runtime credential denial of raw history and owner operations.