Everything in these pages was read off the running server via an authenticated
initialize + tools/list handshake and safe validation probes. Tool names, signatures,
enum values, annotations, response envelopes, and error codes come from the live server —
not hand-maintained prose. If any other documentation disagrees, trust the server (see
Regenerate this reference).At a glance
Connect your client
Add Reply MCP to Claude, Cursor, or any MCP client in a couple of minutes.
Tool reference
The full catalog of all 70 tools, grouped by domain.
Tool contract & errors
The rules every tool enforces: schemas, envelopes, error codes, retries.
Building agents
Design principles, high-stakes gating, and a drop-in system prompt.
Guides: what to build
Task-based guides — launch outreach, process replies, build an AI SDR.
Choose your interface
Not sure MCP is the right surface? Compare MCP, Skills, CLI, and API.
What’s exposed
The 70 tools cover the day-to-day Reply.io surface an agent needs:
See the tool reference for every tool name, its safety annotation, and a one-line purpose.
MCP vs the REST API
MCP and the REST API are two surfaces over one product — same account, same credit system.- MCP — the interactive surface. 70 curated, annotated tools for agent actions and natural-language workflows. Best for day-to-day operations.
- REST (
https://api.reply.io/v3) — the exhaustive surface. Use it for bulk imports and updates, background jobs, deep report exports, webhooks, and template/schedule/mailbox management not exposed as tools.
REST API reference
Browse the full v3 REST API — the exhaustive surface for bulk and background operations.
FAQ
Is the MCP server real, and how current is this page?
Is the MCP server real, and how current is this page?
Yes — it’s an official, live server at
mcp.reply.io. These pages were generated from an
authenticated initialize + tools/list handshake against the running server. If the
server ever returns a different tool set, the server is newer — trust it, and
regenerate the reference in seconds.How does authentication work?
How does authentication work?
Pass your Reply.io API key as an
Authorization: Bearer header. A call with
no credentials returns 401 with a WWW-Authenticate challenge; OAuth protected-resource
metadata is also published for clients that prefer a discovery-based flow. See
Connect.How do I know which tools are safe to call?
How do I know which tools are safe to call?
Every tool is annotated in
tools/list: 31 are readOnlyHint: true and 39 are
destructiveHint: true. Agents can — and should — gate on these annotations before adding
their own confirmation UX for the high-stakes subset. See the
tool contract.What do responses look like?
What do responses look like?
Responses are SSE frames; read the last
data: frame. A successful tools/call returns the
payload as a JSON string in result.content[0].text. Tool failures are not HTTP errors —
they arrive as HTTP 200 with result.isError = true. See
response envelopes.When should an agent use MCP instead of the REST API?
When should an agent use MCP instead of the REST API?
Use MCP for interactive, natural-language workflows and everyday operations. Drop to the
REST API for bulk imports/updates, background jobs, report exports, and anything absent from
tools/list.Is the Jason AI SDR autopilot really callable here?
Is the Jason AI SDR autopilot really callable here?
Yes. 31 of the 70 tools drive Jason — the approval queue, knowledge bases, reply handlers,
reengagement cards, offers, playbooks, and the Review/Autonomous reply mode.