> ## 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. # Get add-card link > Return a temporary Paddle Customer Portal deep link to add or replace a card for the workspace's applied subscription. This is the ONLY way to add a card: Paddle has no add-card API; the user enters card details on Paddle's hosted page. Never cached. Returns no_billing_account if the workspace has no applied subscription. Requires billing.manage. Contract: - MCP tool `get_billing_payment_method_add_link`, registry package `mcp.id/billing_payment_methods`, mount `id.billing`. - Operation `action`, response envelope `action`. - Flags: read only. ## OpenAPI ````yaml /api-reference/id/openapi.yaml post /api/billing-payment-methods/get-add-link openapi: 3.0.3 info: title: 'GTM API public contract: gtm.service.id' description: >- Identity, access and money: users, teams and members, API keys, OAuth clients and authorizations, billing products, subscriptions, transactions and payment methods, the credit ledger, notifications, TLS certificates, observability and support requests. 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.id`, 77 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/id/v4 description: Production, through the app.gtm-api.com gateway - url: http://localhost:8021 description: Local Docker (gtm_id_nginx_dev) security: - BearerJwt: [] TeamSid: [] tags: - name: account_shares description: Registry package `mcp.id/account_shares`, served on MCP mount `id.access`. - name: api_keys description: Registry package `mcp.id/api_keys`, served on MCP mount `id.access`. - name: billing_payment_methods description: >- Registry package `mcp.id/billing_payment_methods`, served on MCP mount `id.billing`. - name: billing_products description: >- Registry package `mcp.id/billing_products`, served on MCP mount `id.billing`. - name: billing_subscriptions description: >- Registry package `mcp.id/billing_subscriptions`, served on MCP mount `id.billing`. - name: billing_transactions description: >- Registry package `mcp.id/billing_transactions`, served on MCP mount `id.billing`. - name: credit_transactions description: >- Registry package `mcp.id/credit_transactions`, served on MCP mount `id.credits`. - name: notifications description: >- Registry package `mcp.id/notifications`, served on MCP mount `id.platform`. - name: oauth_authorizations description: >- Registry package `mcp.id/oauth_authorizations`, served on MCP mount `id.access`. - name: oauth_clients description: Registry package `mcp.id/oauth_clients`, served on MCP mount `id.access`. - name: observability_requests description: >- Registry package `mcp.id/observability_requests`, served on MCP mount `id.platform`. - name: sessions description: Registry package `mcp.id/sessions`, served on MCP mount `id.identity`. - name: ssl_certificates description: >- Registry package `mcp.id/ssl_certificates`, served on MCP mount `id.platform`. - name: support_requests description: >- Registry package `mcp.id/support_requests`, served on MCP mount `id.platform`. - name: team_members description: Registry package `mcp.id/team_members`, served on MCP mount `id.identity`. - name: teams description: Registry package `mcp.id/teams`, served on MCP mount `id.identity`. - name: users description: Registry package `mcp.id/users`, served on MCP mount `id.identity`. paths: /api/billing-payment-methods/get-add-link: post: tags: - billing_payment_methods summary: Get add-card link description: >- Return a temporary Paddle Customer Portal deep link to add or replace a card for the workspace's applied subscription. This is the ONLY way to add a card: Paddle has no add-card API; the user enters card details on Paddle's hosted page. Never cached. Returns no_billing_account if the workspace has no applied subscription. Requires billing.manage. Contract: - MCP tool `get_billing_payment_method_add_link`, registry package `mcp.id/billing_payment_methods`, mount `id.billing`. - Operation `action`, response envelope `action`. - Flags: read only. operationId: get_billing_payment_method_add_link responses: '200': description: '`action` success envelope.' content: application/json: schema: $ref: '#/components/schemas/GetBillingPaymentMethodAddLinkResponse' 4XX: $ref: '#/components/responses/McpClientError' 5XX: $ref: '#/components/responses/McpServerError' components: schemas: GetBillingPaymentMethodAddLinkResponse: type: object properties: success: type: boolean enum: - true operation: type: string enum: - action action: type: string description: kebab-case verb; matches the route segment. item: {} result: type: object properties: add_link: type: string nullable: true expires_at: type: string subscription_sid: type: string required: - add_link - expires_at - subscription_sid meta: type: object properties: trace_id: type: string description: UUID v7; same 128-bit value as the X-Trace-Id header. span_id: type: string pattern: ^[0-9a-f]{16}$ 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. ````