list_calls

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

Annotations cover the safety profile (readOnlyHint, idempotentHint), so the description adds value with the non-obvious silent-ignore behavior: status/direction/search are dropped when agent_id or number_id is supplied. It also discloses the returned summary fields, which matters since there is no output schema.

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?

Three short sentences, front-loaded with the primary action, then the scoping rule, then return contents. Every sentence carries load and nothing is padded.

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 7-param, all-optional listing tool with no output schema, the description covers the tricky parameter interaction and the shape of the results. Pagination behavior (limit/offset) is left entirely to the schema, but that is a minor omission.

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 coverage is 100%, so the baseline would be 3, but the description contributes the mutual-exclusivity rule between scoping parameters and filter parameters that the schema does not express. That is genuine added meaning beyond per-field descriptions.

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?

States a specific verb and resource ('List recent calls') and enumerates the scoping/filtering dimensions available. It is clearly distinguishable from the sibling get_call (single call) by its listing nature, though it does not name siblings explicitly.

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?

Gives explicit routing between two modes: scope by agent_id/number_id, or filter globally with status/direction/search. It further states the when-not case (filters are ignored when scoping params are present), which is exactly the guidance an agent needs. No named alternative functions, but the selection rule is clear.

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