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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds content the annotations cannot: that the response is the full detail for one call and includes the carrying identity and provider — meaningful because 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?

A single well-formed sentence with the action front-loaded and no filler. It is efficient, though it is lean enough that a short second clause on ID origin or return shape would not have hurt.

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 one-parameter read tool whose annotations already carry the full safety profile, this is close to sufficient: it says what comes back and that the call is located by ID. The residual gap is guidance on where the call_id comes from and how it compares to search_calls.

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 0% for the single parameter, so the description must carry the burden. It names call_id and frames it as the record identifier, but adds no format, source, or validity guidance beyond what the raw schema type already shows.

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 ('Returns full detail for one phone call') and scopes it to a single record via call_id, which implicitly separates it from the sibling search_calls. It never names a sibling, so the differentiation is inferred rather than stated.

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?

'Identified by call_id' implies the agent must already hold an ID (e.g. from search_calls) before calling, which is reasonable implied usage. However, there is no explicit when-to-use statement, no exclusion against list-style siblings, and no note on what to do if the ID is unknown.

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