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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely new behavior: a 404 for calls in conversations you cannot open, and per-type feature gating. It does not explain return format, but that is partially inferable from the field enum.

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?

Front-loaded with the action, then the 404 and feature requirements in two short, purposeful clauses. 'One call from the history' is mildly redundant with 'Get a call' but earns its place by clarifying cardinality.

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 2-parameter read tool with annotations and no output schema, the description covers access failure behavior and feature prerequisites. The field-selection parameter's enum implicitly conveys the returnable shape, so nothing critical is missing, though return/pagination behavior is unstated.

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%, so both 'id' and 'fields' are fully documented in the schema and the baseline is 3. The description adds no extra syntax, format, or constraint detail about either parameter.

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 (get a call) and clarifies cardinality with 'One call from the history,' which implicitly separates it from the sibling list_calls. It does not explicitly name or contrast with that sibling, so it stops short of a 5.

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?

Usage is only implied: the singular 'one call' and the required id parameter signal a single-record lookup, and the feature requirements ('whatsapp_calling', 'voice_agents') hint at applicability. However, there is no explicit when-to-use versus list_calls, and no stated preconditions beyond feature flags.

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