> ## Documentation Index > Fetch the complete documentation index at: https://docs.2501.ai/llms.txt > Use this file to discover all available pages before exploring further. # Check an assigned plugin connection > Checks that the engine can reach an assigned plugin. A failed check returns 200 with safe failure categories; an unavailable engine returns ENGINE_ERROR. - **MCP server**: the engine connects with anonymous access, the Bearer or API key credential the plugin sends or its valid OAuth authorization, lists the tools without calling them, then closes the client. The credential and its resolved value are checked again before success. - **HTTP API on Main executor**: the engine opens a connection to the base URL, sends no request and uses no credential; tool_count is 0. - **HTTP API on a cluster**: not checked here, and the result is a failure. Check it from the plugin page in Command Center, where the check runs in the cluster. - **Disabled assignments** may be checked without enabling them, except a hosted MCP server: the check starts it, so only a tenant-level administrator may check one that is turned off (403). ## OpenAPI ````yaml /0.18/openapi.json post /api/v1/agents/{id}/plugins/{pluginId}/check openapi: 3.0.3 info: title: 2501 Public API version: v1 description: >- The stable, versioned HTTP API for driving 2501 as code. See the API Overview for authentication, the org_id rule, cursor pagination, and the error envelope. servers: - url: https://{command_center_host} variables: command_center_host: default: your-command-center-host description: Your Command Center host security: - bearerAuth: [] paths: /api/v1/agents/{id}/plugins/{pluginId}/check: post: tags: - Agents summary: Check an assigned plugin connection description: >- Checks that the engine can reach an assigned plugin. A failed check returns 200 with safe failure categories; an unavailable engine returns ENGINE_ERROR. - **MCP server**: the engine connects with anonymous access, the Bearer or API key credential the plugin sends or its valid OAuth authorization, lists the tools without calling them, then closes the client. The credential and its resolved value are checked again before success. - **HTTP API on Main executor**: the engine opens a connection to the base URL, sends no request and uses no credential; tool_count is 0. - **HTTP API on a cluster**: not checked here, and the result is a failure. Check it from the plugin page in Command Center, where the check runs in the cluster. - **Disabled assignments** may be checked without enabling them, except a hosted MCP server: the check starts it, so only a tenant-level administrator may check one that is turned off (403). parameters: - schema: type: string required: true name: id in: path - schema: type: string required: true name: pluginId in: path requestBody: required: true content: application/json: schema: type: object properties: {} default: {} additionalProperties: false responses: '200': description: Connection check result content: application/json: schema: oneOf: - type: object properties: agent_id: type: string plugin_id: type: string checked_at: type: string format: date-time success: type: boolean enum: - true tool_count: type: integer minimum: 0 description: The tools the MCP server lists; 0 for an HTTP API. account_name: type: string description: >- For an OAuth plugin, who the connected account signs in as. transport: type: string enum: - streamable-http - http-sse description: The transport a remote MCP server answered on. protocol_version: type: string description: The MCP protocol version the server agreed to. required: - agent_id - plugin_id - checked_at - success - tool_count - type: object properties: agent_id: type: string plugin_id: type: string checked_at: type: string format: date-time success: type: boolean enum: - false failures: type: array items: type: string enum: - migration_required - invalid_configuration - connection_or_discovery_failed - tool_budget_exceeded - cleartext_not_allowed - destination_not_allowed - redirect_not_followed - access_check_failed - credential_unavailable - authorization_required - authentication_failed - image_unavailable - assignment_changed - cleanup_failed - hosted_server_starting - hosted_server_start_failed minItems: 1 description: Why the check failed, as safe categories. detail: type: string maxLength: 500 description: >- What went wrong, when the engine can say more than the category: an HTTP status, a DNS or TLS failure, or a hosted MCP server start error such as an image that cannot be pulled, a used-up quota or a missing permission. required: - agent_id - plugin_id - checked_at - success - failures '400': description: >- Bad request - a field is missing, malformed, or not allowed (VALIDATION_FAILED, BAD_REQUEST, INVALID_CURSOR) content: application/json: schema: $ref: '#/components/schemas/Error' '401': description: >- No credentials, or a key that is invalid, revoked, or expired (UNAUTHORIZED) content: application/json: schema: $ref: '#/components/schemas/Error' '403': description: >- Authenticated but not allowed (FORBIDDEN, ORG_ACCESS_DENIED, STEP_UP_REFUSED, TWO_FACTOR_ENROLLMENT_REQUIRED, LICENSE_CAP_REACHED, LICENSE_EXPIRED) content: application/json: schema: $ref: '#/components/schemas/Error' '404': description: No such row that this caller can see (NOT_FOUND) content: application/json: schema: $ref: '#/components/schemas/Error' '500': description: Server or engine error (INTERNAL_ERROR, ENGINE_ERROR) content: application/json: schema: $ref: '#/components/schemas/Error' components: schemas: Error: type: object properties: code: type: string example: VALIDATION_FAILED message: type: string example: Validation failed request_id: type: string example: req_3702b7e7-... field: type: string description: Set when one input is at fault errors: type: array items: type: object properties: field: type: string message: type: string required: - field - message description: Set when several inputs are at fault details: type: object additionalProperties: nullable: true required: - code - message - request_id securitySchemes: bearerAuth: type: http scheme: bearer description: >- An API key minted in Command Center (Settings -> API Keys), sent as `Authorization: Bearer 2501_ak_...`. A Command Center session cookie is also accepted. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.