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Signal MCP

by googlarz
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Python
Local

receive_messages

Poll the Signal daemon once for new messages and save them locally. Use when the daemon is stuck or other retrieval methods fail.

Instructions

Poll the signal-cli daemon once for newly arrived messages and save them to the local store. Normally use get_unread instead — it polls when needed and returns unread messages in one call; use receive_direct only if the daemon is stuck. timeout: seconds to wait (integer, default 5); max_messages: stop after this many (default: no limit). Incoming edits and remote deletes are applied to stored messages instead of being returned; receipts are returned but not stored. Does not mark anything read. Returns a list of messages (id, sender, sender_name, recipient, group_id, group_name, body, timestamp, attachments, quote_id, reactions, is_read). If the background service already holds the receive lock, returns {note, messages} with up to 50 unread messages from the store instead.

Input Schema

NameRequiredDescriptionDefault
timeoutNoSeconds to wait for messages (default: 5)
max_messagesNoReturn after this many messages (default: no limit)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.40.1
    • addedInput schema / properties / max_messages
      Added value: +{
+  "description": "Return after this many messages (default: no limit)",
+  "type": "integer"
+}
  2. First observedv0.1.0

TDQS

A4.6/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations provide only generic hints (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false). The description adds substantial non-obvious behavior: edits and remote deletes are applied to stored messages rather than returned, receipts are returned but not stored, nothing is marked read, and a fallback shape {note, messages} is returned if the receive lock is held. This is exactly the kind of context annotations cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Dense and front-loaded: behavior, routing, parameters, side effects, and return shape in a compact block. Every sentence carries signal, though the return-field enumeration is a long list that slightly taxes readability.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a non-idempotent, open-world polling tool with no output schema, the description covers side effects (what is stored vs returned, edits/deletes applied, nothing marked read), the return shape, and the lock-contention fallback. Nothing an agent needs to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents timeout and max_messages. The description restates the defaults but adds no syntax or constraint details beyond the schema. Baseline 3 for full schema coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Poll the signal-cli daemon once for newly arrived messages and save them to the local store') and explicitly differentiates from siblings get_unread and receive_direct, with a clear default preferred path.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly states when to use this vs alternatives: 'Normally use get_unread instead', and 'use receive_direct only if the daemon is stuck'. This is textbook when/when-not/alternatives guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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