signal-cli-mcp

proposeSignalMessage

Propose sending a Signal message to a specific recipient, then hold for human approval in a local GUI; nothing is transmitted without explicit consent.

Instructions

Proposes sending a Signal message to an individual. AWAITS human approval in a local GUI — the call may take several minutes. This is not an error; wait patiently. Nothing is sent without approval.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "recipient": "<recipient>",
      "text": "<text>"
    },
    "name": "proposeSignalMessage"
  }
}

Input Schema

Name	Required	Description
`text`	Yes	Message text.
`reason`	No	Short rationale for the proposal, shown to the user.
`recipient`	Yes	Recipient: a contact name (exact, case-insensitive) or an E.164 phone number (e.g. +1...). The server resolves a name to a number; if no contact or several match, the call fails so you can disambiguate.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.1Aug 6, 2026

TDQS

A4.5/5.0

Behavior5/5

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

With no annotations, the description carries full responsibility for behavioral disclosure. It explicitly warns that the call awaits human approval in a local GUI, may take several minutes, is not an error, and that nothing is sent without approval. This fully covers the tool's non-obvious behavior.

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

Conciseness5/5

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

The description is two concise sentences that front-load the key purpose and the critical behavioral warning. Every sentence adds necessary information, and there is no wasted text.

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?

Despite having no output schema or annotations, the description covers the essential context: purpose, recipient scope, approval workflow, duration warning, and the guarantee that nothing is sent without approval. Parameter details are fully handled by the schema, so no significant gaps remain.

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?

The input schema provides 100% coverage with meaningful descriptions for all three parameters, including recipient resolution and failure conditions. The description itself adds no parameter-level details, but since the schema is thorough, a baseline of 3 is appropriate.

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?

The description clearly states a specific action ('Proposes sending a Signal message to an individual') and differentiates it from sibling tools that target groups or group creation. The verb 'propose' and resource 'individual message' are unambiguous.

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

Usage Guidelines4/5

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

The description gives clear context by specifying 'to an individual,' which implies this tool is for person-to-person messages rather than group messages. It does not explicitly name alternatives or when-not-to-use, but the sibling tool names and the individual/group contrast provide enough 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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