curl https://api.texttree.ai/api/v1/messages \
  -H "Authorization: Bearer $TEXTREE_ACCESS_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"phone_number":"+15551234567","body":"Hello"}'

OpenAI MCP Compatibility

TextTree exposes a native MCP endpoint that can be used by OpenAI-compatible MCP clients:

https://api.texttree.ai/mcp

The endpoint uses stateless Streamable HTTP. Send JSON-RPC messages with POST /mcp, Authorization: Bearer $TEXTREE_ACCESS_TOKEN, Accept: application/json, text/event-stream, and Content-Type: application/json. GET /mcp and DELETE /mcp return 405 because TextTree does not allocate server-side MCP sessions.

OAuth discovery

TextTree publishes MCP OAuth discovery metadata at:

• https://api.texttree.ai/.well-known/oauth-protected-resource/mcp
• https://api.texttree.ai/.well-known/oauth-authorization-server/mcp

OAuth clients use authorization code with PKCE S256 and the MCP resource https://api.texttree.ai/mcp. Bearer tokens can be audience-bound to that MCP resource. Audience-free tokens remain accepted for compatibility.

Protocol versions

TextTree currently supports:

• 2025-11-25
• 2025-06-18
• 2025-03-26

The server advertises capabilities for tools, prompts, resources, and completions. initialize returns TextTree-specific instructions that tell agents to read onboarding and billing resources, collect explicit real-world targets before onboarding, and only call messages.send with recipient-approved SMS and a stable idempotency key.

JSON-RPC methods

The native MCP endpoint accepts these JSON-RPC methods:

Method	Purpose
initialize	Starts the MCP handshake and returns the protocol version, capabilities, server info, and instructions.
notifications/initialized	Marks the client as ready after initialization.
ping	Checks endpoint liveness.
tools/list	Lists available tool descriptors.
tools/call	Executes a tool by name.
resources/list	Lists static resources.
resources/templates/list	Lists resource templates.
resources/read	Reads a resource by URI.
prompts/list	Lists available prompts.
prompts/get	Fetches a prompt by name.
completion/complete	Returns argument completions for path, sender path, and region values.

notifications/initialized and other notifications/* messages receive no response. As noted above, GET /mcp and DELETE /mcp return 405.

Tools

The current tool registry is:

Tool	Scope	Purpose
messages.send	messages:write	Queue an outbound SMS through the same messaging path as /api/v1/messages.
onboarding.status	onboarding:read	Inspect onboarding, balance, invoice, and SMS readiness state.
onboarding.create_invoice	onboarding:write	Create or reuse a launch funding invoice.
onboarding.invoice_status	onboarding:read	Check funding invoice status.
onboarding.test_sms	onboarding:write	Send the fixed Fast Send onboarding test SMS.
onboarding.request_dedicated_number	onboarding:write	Submit business details for the recommended Dedicated Number path.

Tool calls through native MCP require mcp:execute plus any tool-specific scope. The legacy REST route POST /mcp/tools/:name also requires mcp:execute plus the tool-specific scope.

Tool descriptor structure

tools/list returns descriptors with:

• name, title, and description
• JSON Schema 2020-12 inputSchema
• JSON Schema 2020-12 outputSchema
• MCP annotations: readOnlyHint, destructiveHint, idempotentHint, and openWorldHint
• _meta["texttree/required_scope"]
• _meta["texttree/timeout_ms"]

OpenAI Apps SDK UI widget fields are not currently provided. TextTree does not ship an Apps SDK web component, so descriptors do not include _meta.ui.resourceUri or _meta["openai/outputTemplate"]. If TextTree adds a ChatGPT app UI later, those fields should point to the UI template resource and the descriptors should mirror any securitySchemes needed by older clients.

Prompts

Current MCP prompts:

• texttree.onboard_agent
  • arguments: path (dedicated_number or fast_send), region
  • purpose: guide an agent through Dedicated Number or Fast Send onboarding
• texttree.first_send
  • arguments: recipient_context, sender_path (dedicated_number or fast_send)
  • purpose: prepare a safe first SMS send after onboarding and funding

Prompt completions are available for path, sender path, and region arguments.

Resources and templates

Current resources:

• texttree://mcp/tools
• texttree://onboarding/status
• texttree://billing/status
• texttree://messages/recent

Current resource templates:

• texttree://invoices/{id}
• texttree://messages/{id}
• texttree://numbers/{id}
• texttree://onboarding/checklist
• texttree://billing/readiness
• texttree://elicitations/{correlation_id}

Resource reads enforce their resource-specific TextTree scopes before returning data.

Safety model

messages.send is the only current MCP tool that queues an outbound SMS. It is marked as destructive and open-world, requires messages:write, and runs through the same suppression, spend, sender-readiness, and delivery-worker gates as POST /api/v1/messages.