Retrieve phone numbers from ElevenLabs to manage telephony resources. Filter by agent ID, provider, or branch ID.
List Phone Numbers
| Name | Required | Description | Default |
|---|---|---|---|
| agent_id | No | Filter by assigned agent ID | |
| provider | No | Filter by telephony provider | |
| branch_id | No | Filter by assigned branch ID |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so safety semantics are covered structurally. The description adds nothing beyond that — no mention of pagination, result limits, default ordering, or scope of the listing.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The single phrase is brief but not concise in the useful sense — it is underspecified rather than economical, providing no information an agent could act on beyond the name itself.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a list endpoint with no output schema, the description should at least hint at return shape, filtering behavior, or pagination. Neither the description nor an output schema tells the agent what comes back, leaving a real gap despite the well-covered input schema and annotations.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, with each of the three optional filters (agent_id, provider, branch_id) documented inline, so the baseline of 3 applies. The description contributes no additional parameter meaning beyond the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description is a verbatim restatement of the tool name ('List Phone Numbers' = list_phone_numbers_route), which the rubric classifies as tautology territory. It does convey a read/list operation, but adds no scope, resource detail, or differentiation from siblings like get_phone_number_route or create_phone_number_route.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
There is no guidance on when to use this tool versus get_phone_number_route (single lookup) or create/update/delete variants, nor any mention that the three filters can be combined. The agent must infer usage entirely from the name.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.