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Send an MCP message to an upstream MCP server through the Gate

POST
/mcp/{connector}
curl --request POST \
  --url http://127.0.0.1:8080/mcp/example \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'Deedglass-Version: 2026-10-01' \
  --data '{ "jsonrpc": "2.0", "id": 1, "method": "tools/list" }'

The MCP Streamable HTTP gateway (S15) for one upstream MCP server configured under mcp.upstreams.<connector> in deedglass.yaml. Deedglass runs every allowed tools/call itself (gateway mode) and holds the upstream’s credentials. A POST-only JSON-RPC endpoint, sessionless and dual-era: 2026-07-28 requests carry _meta io.modelcontextprotocol/protocolVersion and the MCP-Protocol-Version, Mcp-Method and (for tools/call, resources/read, prompts/get) Mcp-Name headers, and any Mcp-Param-* a tool’s x-mcp-header declares; a missing or different header is 400 with JSON-RPC -32020, an unsupported version 400 with -32022 and data.supported. Legacy clients (2025-11-25, 2025-06-18, 2025-03-26) open with initialize; no Mcp-Session-Id is minted, and one sent is ignored. Notifications get 202 with no body. An unknown method is 404 (modern) or 200 (legacy) with -32601. Responses are application/json with Cache-Control: no-store; an Accept without application/json is 406. Errors before the message is read are JSON-RPC errors without an id whose data names the Deedglass error code, doc_url and request_id: 401 with WWW-Authenticate: Bearer realm="deedglass", resource_metadata="<base>/.well-known/oauth-protected-resource/mcp/<connector>", scope="actions:execute", 413 over 4 MiB, 415 for another Content-Type, 429 beyond 32 requests in flight per agent. A browser Origin other than the server’s own or one in mcp.allowed_origins gets 403. A stopped or suspended agent’s tools/call is recorded and sealed, and answered as an isError tool result. GET and DELETE get 405 with Allow: POST. Idempotency-Key is ignored. An agent key with actions:execute. JSON-RPC is not modelled here; see docs/MCP.md.

Authorizations

Section titled “Authorizations”

Parameters

Section titled “Parameters”

Path Parameters

Section titled “Path Parameters”
connector
required
string
/^([a-z][a-z0-9-]{1,31}|con_[0-7][0-9a-hjkmnp-tv-z]{25})$/

The upstream’s connector name (mcp.upstreams.<name>), or a connector id (con_…) from S16.

Header Parameters

Section titled “Header Parameters”
Deedglass-Version
string
/^[0-9]{4}-[0-9]{2}-[0-9]{2}$/

The API version (YYYY-MM-DD). Leave it out to use your org’s pinned version (public routes use the latest). An unknown version is 400 api_version_invalid.

Request Bodyrequired

Section titled “Request Bodyrequired”

A JSON-RPC 2.0 message.

Media typeapplication/json
object
Example
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Responses

Section titled “Responses”

200

Section titled “200”

One JSON-RPC response (a result, or an error such as -32601 for a legacy unknown method).

Media typeapplication/json
object
Example
{
  "jsonrpc": "2.0",
  "id": 3,
  "result": {
    "resultType": "complete",
    "content": [
      {
        "type": "text",
        "text": "Echo: hello"
      }
    ],
    "isError": false,
    "_meta": {
      "com.deedglass/action": "act_01k6w4a3d5f7h9k1n3q5s7v9x1",
      "com.deedglass/deed": "deed_01k6w4a3d5f7h9k1n3q5s7v9x2"
    }
  }
}

Headers

Section titled “Headers”
Deedglass-Request-Id
string
/^req_[0-7][0-9a-hjkmnp-tv-z]{25}$/

This request’s id. Quote it to support; it matches error.request_id.

202

Section titled “202”

A notification was accepted. No body.

400

Section titled “400”

A header that doesn’t match the body (-32020 HeaderMismatch), an unsupported protocol version (-32022 with data.supported and data.requested), a batch or a response (-32600), or JSON that can’t be parsed (-32700).

Media typeapplication/json

A JSON-RPC 2.0 error response.

object
jsonrpc
required
string
Allowed value: 2.0
id
string | number | null
error
required
object
code
required
integer
message
required
string
Example
{
  "jsonrpc": "2.0",
  "id": 3,
  "error": {
    "code": -32020,
    "message": "Header mismatch: Mcp-Name is \"echo\" but the body names \"delete_all\". Send the same tool name in both."
  }
}

Headers

Section titled “Headers”
Deedglass-Request-Id
string
/^req_[0-7][0-9a-hjkmnp-tv-z]{25}$/

This request’s id. Quote it to support; it matches error.request_id.

403

Section titled “403”

A browser Origin other than the server’s own: a JSON-RPC error without an id (DNS-rebinding protection). A key without actions:execute, or a stopped or suspended agent, also gets 403, with the error envelope.

Media typeapplication/json

A JSON-RPC 2.0 error response.

object
jsonrpc
required
string
Allowed value: 2.0
id
string | number | null
error
required
object
code
required
integer
message
required
string
Example
{
  "jsonrpc": "2.0"
}

Headers

Section titled “Headers”
Deedglass-Request-Id
string
/^req_[0-7][0-9a-hjkmnp-tv-z]{25}$/

This request’s id. Quote it to support; it matches error.request_id.

default

Section titled “default”

An error. Every error has this envelope; doc_url explains the code.

Media typeapplication/json
object
error
required
object
type
required
string
Allowed values: invalid_request_error authentication_error permission_error policy_error rate_limit_error api_error
code
required
string
Allowed values: invalid_api_key api_key_revoked api_key_expired agent_suspended agent_stopped org_stopped insufficient_scope policy_denied approval_required approval_expired budget_exceeded intent_required intent_invalid intent_replay tool_unknown connector_unavailable upstream_error timeout rate_limited idempotency_conflict validation_failed not_found conflict internal_error authentication_required method_not_allowed request_too_large unsupported_media_type invalid_json api_version_invalid idempotency_key_invalid idempotency_key_in_use service_unavailable session_expired csrf_failed insufficient_role login_link_invalid login_code_invalid last_owner policy_unavailable policy_invalid credentials_missing destination_blocked vault_unavailable upstream_auth_failed upstream_not_found upstream_rate_limited response_too_large statement_refused row_limit_exceeded database_role_unsafe database_not_ready witness_not_configured approval_decided already_countersigned approver_not_eligible self_approval approval_needs_person context_changed approval_unsatisfiable approval_link_invalid approval_link_review_only approver_unmapped stripe_live_key_refused stripe_livemode_detected upstream_approval_pending schedule_needs_approval action_executing from_denied undo_unavailable undo_plan_stale already_undone undo_conflict replay_too_large replay_window_invalid suggestion_stale shadow_slot_taken suggestion_decided observe_not_enabled pro_required
message
required

One or more calm sentences with the next step.

string
param
required

The request field, query parameter or header the error is about.

string | null
request_id
required
string
/^req_[0-7][0-9a-hjkmnp-tv-z]{25}$/
doc_url
required
string format: uri
diagnostics

On policy_invalid only. Each problem with its line, code and hint.

Array<object>

One finding about a policy file, with its position and the next step. Codes are stable and listed in docs/POLICY_ERRORS.md. In the policy_invalid error envelope each diagnostic also carries object: policy_diagnostic. The full PolicyDiagnostic schema is in openapi.yaml.

object
action

One agent action. Its sections mirror the deed’s. status is the one field an agent needs; state is the exact lifecycle state (docs/GATE.md). The Gate’s own responses (POST /v1/actions and its result report) add execution.result and witness.reasons; lists leave both out. The full Action schema is in openapi.yaml.

object
checks

On undo_unavailable only. Every check of the undo, each with its fix. Additive (S23).

Array<object>

One of the twelve safety checks (S23 §3.3). Available means no check failed. The full UndoCheck schema is in openapi.yaml.

object
Example
{
  "error": {
    "type": "invalid_request_error",
    "code": "not_found",
    "message": "There's no endpoint at GET /v1/helth. Did you mean /v1/health?",
    "param": null,
    "request_id": "req_01j9zr3m5k8q2w7x4t6v0b1c9d",
    "doc_url": "https://docs.deedglass.com/errors/not_found"
  }
}

Headers

Section titled “Headers”
Deedglass-Request-Id
string
/^req_[0-7][0-9a-hjkmnp-tv-z]{25}$/

This request’s id. Quote it to support; it matches error.request_id.

Deedglass-Version
string

The API version this response follows.