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Signal MCP

by googlarz
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

unblock_contact

Restore messaging and calls from a previously blocked Signal contact by unblocking their number, allowing them to reach you again without notifying them.

Instructions

Unblock a previously blocked Signal contact, restoring their ability to send you messages and calls. Only works when signal-mcp is the account's primary device — fails with 'This command doesn't work on linked devices' if signal-mcp was set up via signal-cli link. The contact is NOT notified that they were unblocked. Use block_contact to re-block, or list_contacts to see which contacts are blocked.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
numberYesPhone number to unblock (E.164 format)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.1.2
    • changedInput schema / properties / number / description
      Previous value: -"Phone number to unblock"New value: +"Phone number to unblock (E.164 format)"
  2. First observedv0.1.0

TDQS

A4.7/5.0
Behavior5/5

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

With no annotations provided, the description carries the full burden. It discloses the device restriction, the failure mode, and the side effect that the contact is not notified. This goes beyond basic mutation disclosure and covers relevant operational 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 concise and front-loaded with the main action, followed by essential conditions and alternatives. Every sentence serves a purpose with no redundancy or filler.

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 single-parameter mutation tool with no output schema, the description covers the core action, prerequisites, failure behavior, side effects, and related tools. Nothing essential is missing for an agent to use it correctly.

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 schema covers the single parameter fully with a clear description (E.164 format). The description adds no additional semantic meaning beyond the schema, so the baseline of 3 for high schema coverage 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 the action ('Unblock a previously blocked Signal contact') and the resource (Signal contact), and it explicitly distinguishes from the sibling block_contact. The verb and object are specific and unambiguous.

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?

It explicitly states when the tool works (primary device) and when it fails (linked devices), including the exact error message. It also names alternatives: use block_contact to re-block and list_contacts to see blocked contacts. This is thorough guidance for selection and invocation.

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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