> ## Documentation Index > Fetch the complete documentation index at: https://docs.mcpjam.com/llms.txt > Use this file to discover all available pages before exploring further. # Send one agent Playground message > Send one message to a project's MCP servers and get the model's reply plus the telemetry a participant in the conversation could not see: which tools ran, with what arguments, what each returned, per-call latency, and token usage. **Spends model credits per call.** `idempotencyKey` is required and must be STABLE for the triggering intent — a fresh key per HTTP attempt deduplicates nothing, so a timeout-and-retry would run and bill the turn twice. With a stable key, a retry replays the completed turn. Omit `sessionId` to start a session; pass the one this returns to continue it. Configuration (`modelId`, target, `systemPrompt`, `toolMode`) pins on the FIRST turn — a continuation that resends any of it is refused with `details.reason: "CONFIG_ON_CONTINUATION"`. Only sessions created through this endpoint may be continued through it (`CONTINUATION_NOT_ALLOWED`): appending to a human's live Playground session would interleave two writers on one transcript. `toolMode` defaults to `read_only`, which advertises only tools the server annotated `readOnlyHint: true`. That hint is server-asserted, so `read_only` is a policy this host applies, not a guarantee it can verify. `auto` advertises everything and **may cause real external side effects** through arbitrary third-party tools. ## OpenAPI ````yaml /reference/openapi.json post /chat-sessions/messages openapi: 3.1.0 info: title: MCPJam API version: 1.0.0-preview description: >- Programmatic access to MCP servers saved in your MCPJam projects — live diagnostics (validate, inspect, export) and operations: call tools, render prompts, run eval suites asynchronously and poll their results, and import OAuth tokens. **The API is in preview**: the surface may change while we finish the design. Error `code` values are stable; error `message` strings are not. Write clients that ignore unknown response fields. contact: name: MCPJam url: https://github.com/MCPJam/inspector/issues servers: - url: https://app.mcpjam.com/api/v1 description: Hosted MCPJam security: - bearerAuth: [] tags: - name: Hosts description: >- Project hosts: named model + capability profiles you run chats and eval suites against. - name: Environments description: >- Project environments: named, live-editable execution bundles (one host, an optional standalone server group, optionally pinned skills and plugin versions) that eval suites and journeys run against. Distinct from Sandbox images, which are Computer base images. Reads require project membership; every write requires project admin. - name: Plugins description: >- Agent Plugins imported into a project — read-only inventory and version detail. - name: Sandbox images description: >- Custom Computer images: a digest-pinned Dockerfile built into an immutable image your project's computers boot from. - name: Server diagnostics description: Connect-level health checks against a saved MCP server. - name: Primitives description: 'The server''s MCP primitives: tools, prompts, and resources.' - name: Export description: Full-server snapshots for diffing and CI. - name: Execution description: 'Run the server''s primitives: call tools, render prompts.' - name: Eval runs description: >- Asynchronous eval suite runs: create with 202, poll status, iterations, and traces. - name: Conformance runs description: >- Ingest MCP spec-conformance results from the SDK/CLI into project-owned history. Distinct from Eval runs (authored LLM cases) and from directory readiness. - name: Server connections description: >- Connect an MCP server URL to a project, authorizing in a browser when the server requires it. - name: OAuth description: 'Bring-your-own OAuth: import externally obtained tokens for a server.' - name: Scenarios description: >- Read-only access to the scenarios published from a project: listing, settings, attached servers, and share links. - name: Catalog description: >- Discover the resources the other routes operate on: your account, projects, servers, eval suites, and chat sessions. - name: Tunnels description: >- Relay tunnels that expose local MCP servers through a public URL, registered as first-class project servers (the `mcpjam cloud tunnel` CLI flow). - name: Agent description: >- Headless agent turns over the public API: send a message history, the server runs one assistant turn with project-scoped workspace tools (eval reads + suite creation) on a pinned hosted model, and returns the reply plus created-resource references. - name: Swarms description: >- Personas, journeys and swarm containers — the authoring half of Swarms — plus the model-backed generation that drafts them. - name: Swarm runs description: >- Launching journeys and reading what they produced. Launching SPENDS — see the per-operation notes. - name: Swarm insights description: >- What a swarm run revealed. The scorecard and findings are deterministic and free; requesting wave insights runs models and draws on your shared daily ledger. - name: User testing description: >- Publishing an environment for real visitors, and controlling who can reach it. Several of these NARROW access and take effect immediately. - name: Directory readiness description: >- Grade a saved server against a publisher's listing requirements: Anthropic's connector directory or OpenAI's plugin directory. Reported as lane status and coverage, never as a numeric score, and excluded from `pooledConformanceScore`. Deterministic grading is free; model-backed experience observations are an explicit opt-in that consumes MCPJam credits and can never decide a verdict. - name: Registry description: >- Search the scraped MCP directories (Claude, ChatGPT, and any future source), list curated/org registry cards, and install them into a project. Install writes a `servers` row and provenance — it does not open a live session. There is no catalog-uninstall route: delete the project server instead. Directory reads require a bearer (including minted guest tokens) but do not materialize a user. Card/connection reads and all writes are authed-non-guest. paths: /chat-sessions/messages: post: tags: - Chat sessions summary: Send one agent Playground message description: >- Send one message to a project's MCP servers and get the model's reply plus the telemetry a participant in the conversation could not see: which tools ran, with what arguments, what each returned, per-call latency, and token usage. **Spends model credits per call.** `idempotencyKey` is required and must be STABLE for the triggering intent — a fresh key per HTTP attempt deduplicates nothing, so a timeout-and-retry would run and bill the turn twice. With a stable key, a retry replays the completed turn. Omit `sessionId` to start a session; pass the one this returns to continue it. Configuration (`modelId`, target, `systemPrompt`, `toolMode`) pins on the FIRST turn — a continuation that resends any of it is refused with `details.reason: "CONFIG_ON_CONTINUATION"`. Only sessions created through this endpoint may be continued through it (`CONTINUATION_NOT_ALLOWED`): appending to a human's live Playground session would interleave two writers on one transcript. `toolMode` defaults to `read_only`, which advertises only tools the server annotated `readOnlyHint: true`. That hint is server-asserted, so `read_only` is a policy this host applies, not a guarantee it can verify. `auto` advertises everything and **may cause real external side effects** through arbitrary third-party tools. operationId: sendChatMessage requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/SendChatMessageRequest' responses: '200': description: >- The turn ran. `persisted.outcome` reports whether the transcript landed — a turn that ran but failed to persist still spent, so this is a 200 with an honest `persisted` block rather than an error. content: application/json: schema: $ref: '#/components/schemas/ChatTurn' '400': $ref: '#/components/responses/ValidationError' '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' '409': description: >- `details.reason` is one of `TURN_IN_PROGRESS` (another turn holds this session's lease; retry after `details.retryAfterMs`), `CONTINUATION_NOT_ALLOWED`, or `SESSION_VERSION_CONFLICT`. content: application/json: schema: $ref: '#/components/schemas/Error' '422': $ref: '#/components/responses/FeatureNotSupported' '429': $ref: '#/components/responses/RateLimited' '500': $ref: '#/components/responses/InternalError' '502': $ref: '#/components/responses/ServerUnreachable' '504': $ref: '#/components/responses/Timeout' components: schemas: SendChatMessageRequest: type: object required: - idempotencyKey - message additionalProperties: false properties: idempotencyKey: type: string minLength: 1 maxLength: 200 description: >- STABLE identity for this turn's intent — reuse it when retrying. A fresh key per attempt deduplicates nothing and will bill the turn twice. Printable ASCII only. message: type: string minLength: 1 maxLength: 8000 description: The message to send, as the user. projectId: type: string description: Required to START a session; ignored when continuing one. sessionId: type: string description: Continue this session. Omit to start a new one. modelId: type: string description: >- Provider-prefixed model id, e.g. `anthropic/claude-sonnet-5`. Required on a first turn. A BARE id is rejected with `details.reason: "MODEL_AMBIGUOUS"` rather than guessed — an unprefixed id is indistinguishable from a local Ollama model, and guessing would spend on the wrong rail. environmentId: type: string description: >- Target this environment's servers. Mutually exclusive with `serverIds`. First turn only. serverIds: type: array maxItems: 20 items: type: string description: >- Target these project servers. Mutually exclusive with `environmentId`. First turn only. Server CONFIGS are never accepted — only ids the project already holds. systemPrompt: type: string maxLength: 8000 description: First turn only. temperature: type: number minimum: 0 maximum: 2 description: >- First turn only — pinned to the session and reused on every continuation. maxSteps: type: integer minimum: 1 maximum: 16 toolMode: type: string enum: - read_only - auto default: read_only description: >- `read_only` advertises only tools annotated `readOnlyHint: true`. `auto` advertises everything and MAY CAUSE REAL EXTERNAL SIDE EFFECTS. First turn only. allowedServerIds: type: array maxItems: 20 items: type: string description: >- Narrow THIS TURN to a subset of the target's servers. An empty array narrows to none and is rejected — omit the field to use the whole target. Per-turn, not pinned. allowedTools: type: array maxItems: 100 items: type: string description: >- Advertise only these tool names, for THIS TURN. An empty array advertises no tools at all — the same request as `maxToolCalls: 0`. Per-turn, not pinned. maxToolCalls: type: integer minimum: 0 maximum: 16 description: >- Cap the tool calls this turn may make, enforced at DISPATCH rather than by bounding steps (one step can emit several parallel calls). `0` advertises no tools at all. ChatTurn: type: object required: - sessionId - turnId - persisted - origin properties: sessionId: type: - string - 'null' description: >- The one public session id. Pass it back to continue, and to the trace/detail reads. NULL only when the turn ran but its transcript did not persist — which `persisted.outcome` reports, and which must not be read as "nothing happened": the turn already spent. turnId: type: string description: >- Minted by the turn lease and used by the ingest dedupe, so it names the same turn in both. reply: type: string finishReason: type: - string - 'null' toolCalls: type: array items: $ref: '#/components/schemas/ChatTurnToolCall' trace: type: object description: This turn's spans, inline. properties: turnId: type: string spanCount: type: integer spans: type: array items: type: object usage: $ref: '#/components/schemas/TurnUsage' model: type: object properties: id: type: string provider: type: string toolMode: type: string enum: - read_only - auto advertisedToolCount: type: integer description: Tools the model could see this turn. excludedToolCount: type: integer description: Tools the tool policy withheld. persisted: type: object properties: outcome: type: string version: type: integer origin: type: string enum: - api replay: type: boolean description: >- Set when this idempotencyKey replayed an already-completed turn. Nothing was spent. message: type: string Error: type: object required: - code - message properties: code: type: string description: >- Stable, machine-readable error code. New codes may be added over time; treat unknown codes as non-retryable failures unless the HTTP status says otherwise. enum: - UNAUTHORIZED - FORBIDDEN - NOT_FOUND - CONFLICT - VALIDATION_ERROR - RATE_LIMITED - FEATURE_NOT_SUPPORTED - SERVER_UNREACHABLE - TIMEOUT - OAUTH_REQUIRED - INTERNAL_ERROR message: type: string description: >- Human-readable description. May change between releases — don't match on it. details: type: object description: Optional, unstructured context bag. additionalProperties: true ChatTurnToolCall: type: object required: - toolCallId - toolName - input - status properties: toolCallId: type: string toolName: type: string input: description: >- The raw arguments sent, scrubbed of protocol annotations (`_meta`, `$`-prefixed keys) and bounded. status: type: string enum: - ok - error output: description: >- The raw result, scrubbed and bounded. Absent when no result was recorded. errorMessage: type: string truncated: type: boolean description: >- The payload was clipped. Always announced — a silently shortened result an agent believes is complete sends it debugging the wrong thing. TurnUsage: type: object properties: inputTokens: type: integer outputTokens: type: integer totalTokens: type: integer responses: ValidationError: description: Malformed body or parameters. content: application/json: schema: $ref: '#/components/schemas/Error' example: code: VALIDATION_ERROR message: Invalid JSON body Unauthorized: description: >- Missing, invalid, revoked, or orphaned key (`UNAUTHORIZED`) — or the **target MCP server** needs an OAuth grant (`OAUTH_REQUIRED`), which is a property of the server, not your key. content: application/json: schema: $ref: '#/components/schemas/Error' examples: badKey: summary: Invalid or revoked key value: code: UNAUTHORIZED message: Invalid API key oauthRequired: summary: Target server needs an OAuth grant value: code: OAUTH_REQUIRED message: Server requires OAuth authorization Forbidden: description: Key is valid but not allowed to do this. content: application/json: schema: $ref: '#/components/schemas/Error' example: code: FORBIDDEN message: You do not have access to this project NotFound: description: Unknown project, server, or resource. content: application/json: schema: $ref: '#/components/schemas/Error' example: code: NOT_FOUND message: Server not found FeatureNotSupported: description: The target server doesn't support this MCP capability. content: application/json: schema: $ref: '#/components/schemas/Error' example: code: FEATURE_NOT_SUPPORTED message: Server does not support resources RateLimited: description: >- Per-key rate limit exceeded (60 requests/minute sustained, bursts up to 10). Honor `Retry-After` and back off with jitter. headers: Retry-After: description: Seconds to wait before retrying. schema: type: integer content: application/json: schema: $ref: '#/components/schemas/Error' example: code: RATE_LIMITED message: API key rate limit exceeded. Slow down and retry. InternalError: description: Something failed on MCPJam's side. content: application/json: schema: $ref: '#/components/schemas/Error' example: code: INTERNAL_ERROR message: Unexpected internal error ServerUnreachable: description: Could not connect to the target MCP server. content: application/json: schema: $ref: '#/components/schemas/Error' example: code: SERVER_UNREACHABLE message: Failed to connect to server Timeout: description: The target MCP server connected but didn't respond in time. content: application/json: schema: $ref: '#/components/schemas/Error' example: code: TIMEOUT message: Request to server timed out securitySchemes: bearerAuth: type: http scheme: bearer description: >- MCPJam API key (`sk_…`). Create one at [Settings → API keys](https://app.mcpjam.com/settings/api-keys). Guest sessions cannot use the API, and API keys cannot manage other API keys. ````