CallMCP — Phone Call MCP Server

Stop Answering A Number From Your Own Twilio Account

detach_own_twilio_number

DestructiveIdempotent

Stop a voice agent answering a number from the business's own connected Twilio account and put back the call setting (VoiceUrl and VoiceMethod) the number had before it was attached. The number is never released from the account and its text settings are not touched. Requires admin role.

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": {
      "phone_number": "<phone_number>"
    },
    "name": "detach_own_twilio_number"
  }
}

Input Schema

Name	Required	Description	Default
`business_id`	No	Business ID (optional only when the token can access exactly one business).
`phone_number`	Yes	E.164 number to stop answering.

Output Schema

Name	Required	Description
`error`	No	Present when success is false
`success`	Yes	Whether the tool completed successfully
`detached`	No
`restored`	No
`business_id`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 12, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Adds substantial context beyond the annotations: it says exactly what is mutated (VoiceUrl and VoiceMethod reverted to prior values), what is not touched (number not released, text settings unchanged), and the authorization requirement (admin role). This reconciles usefully with destructiveHint=true by framing the mutation as a routing change rather than a release.

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?

Three sentences, front-loaded with the action and backup with the non-effects and permission requirement; every sentence carries information. The first sentence is long with stacked clauses, which costs a little readability, but nothing is wasted.

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 mutation with rich annotations and an output schema, this covers the remaining gaps an agent needs: preconditions (admin role), reversibility semantics (previous settings restored), and blast radius (number retained, text settings untouched). Nothing essential 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 coverage is 100% and both parameters are documented there, including the optional-business_id condition. The description mentions 'E.164' only implicitly ('a number') and adds no format or constraint detail, so it sits at the baseline for a fully documented schema.

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 ('stop a voice agent answering a number from the business's own connected Twilio account') and disambiguates from the plain detach_number sibling by specifying that the number stays in the account and prior VoiceUrl/VoiceMethod are restored. The scope (own Twilio account, not platform-managed numbers) is clear without opening the schema.

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 phrase 'from the business's own connected Twilio account' plus 'put back the call setting ... before it was attached' clearly scopes this to undoing attach_own_twilio_number, implying when to pick this over detach_number. It does not explicitly name the counterpart tool or state exclusions, so it falls just short of a full when/when-not statement.

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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