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

With readOnlyHint=true already providing safety, the description adds value by enumerating the returned fields (id, name, digits, country) and specifying the REST endpoint (GET /numbers). This gives the agent a clearer expectation of the response shape and reinforces the read-only nature.

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 description is two sentences long, front-loads the core purpose ('List the phone numbers owned by the company'), and includes useful inline details (fields and REST endpoint). Every sentence earns its place with no redundancy.

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 simple list tool with paginated parameters, the description adequately covers the purpose, scoping, and return fields. The schema covers pagination details, and annotations cover read-only behavior. It lacks an explicit pointer to sibling tools for single-number retrieval, but this is a minor gap given the simplicity.

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%: both page and per_page have clear descriptions ('1-based page number to fetch (default 1)' and 'Results per page (default 20, max 50)'). The tool description does not add further parameter context, so the baseline of 3 is appropriate.

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 clearly states the tool's action ('List'), resource ('phone numbers owned by the company'), and specifies the returned fields (id, name, digits, country). It distinguishes itself from siblings like aircall_get_number by emphasizing the company-owned scope and the plural listing nature.

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?

The description implies usage for retrieving all company phone numbers but does not explicitly state when to use this tool versus alternatives like aircall_get_number. No exclusion criteria or alternative tool references are provided, so the context is clear but not fully explicit.

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