> ## Documentation Index > Fetch the complete documentation index at: https://docs.gtm-api.com/llms.txt > Use this file to discover all available pages before exploring further. # Create LinkedIn comment > Leave ONE outbound comment on any LinkedIn post, addressed by its activity URN (wire create-comment). Outward and fire-on-success: the post does NOT need to be tracked or owned by us, and nothing is persisted on this service. Identity-bound and non-creditable: linkedin_account_sid REQUIRED, spends the messaging_general bucket, saturation returns 429 with no pool fallback. Reply to an existing comment by passing parent_comment_urn. The comment text comes in text; templates and AI generation are outside this API. Returns the created comment ref plus the activity-log row. To react instead use react_linkedin_post; to read a post's existing comments or commenters use the linkedin-scraping get-post-comments / get-post-commenters tools; to resolve a post URL to its activity URN use get_activity_urn_by_url. Contract: - MCP tool `create_linkedin_comment`, registry package `mcp.linkedin/linkedin_posting`, mount `linkedin.content`. - Operation `action`, response envelope `action`. - Flags: dangerous: the MCP layer gates it behind a preview/commit token, and the effect cannot be undone through this API; mass action: this verb's own request accepts a filter or targets[] set, which the owning service drains. ## OpenAPI ````yaml /api-reference/linkedin/openapi.yaml post /api/linkedin-posting/comment openapi: 3.0.3 info: title: 'GTM API public contract: gtm.service.linkedin' description: >- Connected LinkedIn accounts and everything driven through them: account health and smart limits, conversations and messages, the connection graph, outbound posting, scraping, profile and company enrichment, and the antidetect browsers that execute it all. GENERATED. This document is projected from the Zod MCP tool registry in `product/mcp/gtm.mcp` (one tool per public endpoint, 1:1). Do not edit it by hand; edit the tool definition and regenerate with `pnpm openapi:public`. Surface: the public `/api` contract of `gtm.service.linkedin`, 150 operations. Internal (`/internal`) and health endpoints are deliberately absent; the code-faithful spec that documents those lives in `product/openapi/gtm.openapi.tech`. Conventions: - Auth is a bearer JWT, optionally narrowed by the `Team-SID` header. - Every success body is an MCP envelope: `success: true` plus one typed `operation` shape (`search`, `get`, `create`, `update`, `delete`, `metrics`, `group_by`, `action`), and a `meta` block with `trace_id` for support. - Every failure is the same `McpError` envelope with a code from a fixed 16-code taxonomy, so a client maps errors once. - Lists page with `page_size` (0 to 500, default 50) plus an opaque forward `cursor`; `page_size: 0` returns counts only. - On `GET` and `DELETE`, object-valued query parameters (`filter`, `sort`) travel as JSON text and array-valued ones repeat as `name[]=value`. - The MCP-only `_meta` field (usage analytics) never reaches the backend and is not part of this contract. version: '1.0' contact: name: GTM API url: https://gtm-api.com email: support@gtm-api.com license: name: Proprietary url: https://gtm-api.com/license servers: - url: https://app.gtm-api.com/linkedin/v4 description: Production, through the app.gtm-api.com gateway - url: http://localhost:8020 description: Local Docker (gtm_linkedin_nginx_dev) security: - BearerJwt: [] TeamSid: [] tags: - name: antidetect_browser_logs description: >- Registry package `mcp.linkedin/antidetect_browser_logs`, served on MCP mount `linkedin.browsers`. - name: antidetect_browser_proxies description: >- Registry package `mcp.linkedin/antidetect_browser_proxies`, served on MCP mount `linkedin.browsers`. - name: antidetect_browsers description: >- Registry package `mcp.linkedin/antidetect_browsers`, served on MCP mount `linkedin.browsers`. - name: cloud_browser_sessions description: >- Registry package `mcp.linkedin/cloud_browser_sessions`, served on MCP mount `linkedin.browsers`. - name: cloud_browsers description: >- Registry package `mcp.linkedin/cloud_browsers`, served on MCP mount `linkedin.browsers`. - name: data_requests description: >- Registry package `mcp.linkedin/data_requests`, served on MCP mount `linkedin.data`. - name: linkedin_account_activity_log description: >- Registry package `mcp.linkedin/linkedin_account_activity_log`, served on MCP mount `linkedin.account-monitor`. - name: linkedin_account_block_log description: >- Registry package `mcp.linkedin/linkedin_account_block_log`, served on MCP mount `linkedin.account-monitor`. - name: linkedin_account_quota_hits description: >- Registry package `mcp.linkedin/linkedin_account_quota_hits`, served on MCP mount `linkedin.account-monitor`. - name: linkedin_account_smart_limits description: >- Registry package `mcp.linkedin/linkedin_account_smart_limits`, served on MCP mount `linkedin.accounts`. - name: linkedin_account_snapshots description: >- Registry package `mcp.linkedin/linkedin_account_snapshots`, served on MCP mount `linkedin.account-monitor`. - name: linkedin_account_sync_runs description: >- Registry package `mcp.linkedin/linkedin_account_sync_runs`, served on MCP mount `linkedin.account-monitor`. - name: linkedin_accounts description: >- Registry package `mcp.linkedin/linkedin_accounts`, served on MCP mount `linkedin.accounts`. - name: linkedin_auto_scrape_results description: >- Registry package `mcp.linkedin/linkedin_auto_scrape_results`, served on MCP mount `linkedin.auto-scrapes`. - name: linkedin_auto_scrape_runs description: >- Registry package `mcp.linkedin/linkedin_auto_scrape_runs`, served on MCP mount `linkedin.auto-scrapes`. - name: linkedin_auto_scrapes description: >- Registry package `mcp.linkedin/linkedin_auto_scrapes`, served on MCP mount `linkedin.auto-scrapes`. - name: linkedin_benchmarks description: >- Registry package `mcp.linkedin/linkedin_benchmarks`, served on MCP mount `linkedin.account-monitor`. - name: linkedin_connection_invitations description: >- Registry package `mcp.linkedin/linkedin_connection_invitations`, served on MCP mount `linkedin.network`. - name: linkedin_connection_requests description: >- Registry package `mcp.linkedin/linkedin_connection_requests`, served on MCP mount `linkedin.network`. - name: linkedin_connections description: >- Registry package `mcp.linkedin/linkedin_connections`, served on MCP mount `linkedin.network`. - name: linkedin_conversations description: >- Registry package `mcp.linkedin/linkedin_conversations`, served on MCP mount `linkedin.messaging`. - name: linkedin_custom_requests description: >- Registry package `mcp.linkedin/linkedin_custom_requests`, served on MCP mount `linkedin.platform`. - name: linkedin_enrichment description: >- Registry package `mcp.linkedin/linkedin_enrichment`, served on MCP mount `linkedin.enrichment`. - name: linkedin_followers description: >- Registry package `mcp.linkedin/linkedin_followers`, served on MCP mount `linkedin.network`. - name: linkedin_messages description: >- Registry package `mcp.linkedin/linkedin_messages`, served on MCP mount `linkedin.messaging`. - name: linkedin_posting description: >- Registry package `mcp.linkedin/linkedin_posting`, served on MCP mount `linkedin.content`. - name: linkedin_scraping description: >- Registry package `mcp.linkedin/linkedin_scraping`, served on MCP mount `linkedin.scraping`. paths: /api/linkedin-posting/comment: post: tags: - linkedin_posting summary: Create LinkedIn comment description: >- Leave ONE outbound comment on any LinkedIn post, addressed by its activity URN (wire create-comment). Outward and fire-on-success: the post does NOT need to be tracked or owned by us, and nothing is persisted on this service. Identity-bound and non-creditable: linkedin_account_sid REQUIRED, spends the messaging_general bucket, saturation returns 429 with no pool fallback. Reply to an existing comment by passing parent_comment_urn. The comment text comes in text; templates and AI generation are outside this API. Returns the created comment ref plus the activity-log row. To react instead use react_linkedin_post; to read a post's existing comments or commenters use the linkedin-scraping get-post-comments / get-post-commenters tools; to resolve a post URL to its activity URN use get_activity_urn_by_url. Contract: - MCP tool `create_linkedin_comment`, registry package `mcp.linkedin/linkedin_posting`, mount `linkedin.content`. - Operation `action`, response envelope `action`. - Flags: dangerous: the MCP layer gates it behind a preview/commit token, and the effect cannot be undone through this API; mass action: this verb's own request accepts a filter or targets[] set, which the owning service drains. operationId: create_linkedin_comment requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CreateLinkedinCommentRequest' responses: '200': description: '`action` success envelope.' content: application/json: schema: $ref: '#/components/schemas/CreateLinkedinCommentResponse' 4XX: $ref: '#/components/responses/McpClientError' 5XX: $ref: '#/components/responses/McpServerError' components: schemas: CreateLinkedinCommentRequest: type: object description: Request body of `create_linkedin_comment`. properties: linkedin_account_sid: type: string minLength: 18 maxLength: 18 pattern: ^ln_ac_ description: >- LinkedIn account sid (ln_ac_…), the authoring account. Identity-bound and non-creditable: REQUIRED, never a pool account. activity_urn: type: string minLength: 1 maxLength: 512 description: >- urn:li:activity:, the post handle. The post does NOT need to be tracked or owned by us. Resolve a linkedin.com post URL first with get_activity_urn_by_url. text: type: string minLength: 1 maxLength: 1250 description: The comment body (caller-supplied, no templates or AI in-app). parent_comment_urn: type: string nullable: true maxLength: 512 description: >- Reply target: the comment URN to reply under. Omit or null for a top-level comment. force_dedup: type: boolean nullable: true description: >- Accepted for contract compatibility and NOT enforced by this service today: per-post dedup left with the content trio (gs.service.signals). Passing it changes nothing. required: - linkedin_account_sid - activity_urn - text CreateLinkedinCommentResponse: type: object properties: success: type: boolean enum: - true operation: type: string enum: - action action: type: string description: kebab-case verb; matches the route segment. item: {} result: type: object properties: comment_urn: type: string description: The created comment ref. activity_log: type: object properties: {} description: >- Full dispatch row (linkedin-account-activity-log) per §4.12a. Poll it there by sid for the terminal outcome. required: - comment_urn - activity_log meta: type: object properties: trace_id: type: string description: UUID v7; same 128-bit value as the X-Trace-Id header. span_id: type: string pattern: ^[0-9a-f]{16}$ description: 16 hex chars, root span of this request. timestamp: type: string description: ISO 8601 UTC (Y-m-dTH:i:sZ), response time. duration_ms: type: integer minimum: 0 description: Server-side wall clock. debug_url: type: string description: Deep link to the post-call analysis UI. required: - trace_id - span_id - timestamp - duration_ms - debug_url credits: type: object properties: charged: type: integer minimum: 0 description: Credits debited for THIS call (0 on own-account / cache hit). reason: type: string nullable: true enum: - infra_pool - limit_fallback executed_on: type: string enum: - own_account - infra_pool balance_after: type: integer nullable: true minimum: 0 description: >- Team balance after the debit; null when the ledger was untouched. required: - charged - reason - executed_on - balance_after required: - success - operation - action - item - result - meta McpError: type: object properties: success: type: boolean enum: - false error: type: object properties: code: type: string enum: - validation_failed - nothing_to_update - not_found - relation_not_found - invalid_transition - limit_exceeded - payment_required - duplicate_rejected - conflict - delete_blocked - unauthorized - forbidden - rate_limited - internal_error - service_unavailable - not_implemented message: type: string recoverable: type: boolean suggestion: type: string field_errors: type: object additionalProperties: type: array items: anyOf: - type: string - type: object properties: rule: type: string message: type: string required: - rule - message blockers: type: array items: type: object properties: type: type: string description: >- Machine-readable blocker type (active_flow, pending_tasks, …). severity: type: string enum: - hard - soft description: >- hard = external action required; soft = acknowledge is enough. description: type: string entity_sid: type: string nullable: true count: type: integer resolution: type: string description: 'Hard: tool name to call. Soft: code for acknowledge[].' resolution_hint: type: string required: - type - severity - description - entity_sid - resolution - resolution_hint context: type: object additionalProperties: {} required: - code - message - recoverable meta: type: object properties: trace_id: type: string description: UUID v7; same 128-bit value as the X-Trace-Id header. span_id: type: string pattern: ^[0-9a-f]{16}$ description: 16 hex chars, root span of this request. timestamp: type: string description: ISO 8601 UTC (Y-m-dTH:i:sZ), response time. duration_ms: type: integer minimum: 0 description: Server-side wall clock. debug_url: type: string description: Deep link to the post-call analysis UI. required: - trace_id - span_id - timestamp - duration_ms - debug_url required: - success - error responses: McpClientError: description: >- MCP error envelope. `error.code` is one of validation_failed, nothing_to_update, not_found, relation_not_found, invalid_transition, limit_exceeded, payment_required, duplicate_rejected, conflict, delete_blocked, unauthorized, forbidden, rate_limited, not_implemented. content: application/json: schema: $ref: '#/components/schemas/McpError' McpServerError: description: >- MCP error envelope with `error.code` internal_error or service_unavailable. content: application/json: schema: $ref: '#/components/schemas/McpError' securitySchemes: BearerJwt: type: http scheme: bearer bearerFormat: JWT description: >- Access token issued by gtm.service.id. Its `access_identity` claim carries `team_sid`, `actor_sid` and `actor_type`, and that team scope is authoritative. TeamSid: type: apiKey in: header name: Team-SID description: >- Team scope for tokens that do not carry one. Ignored when the token already names a team. ````