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

The annotations declare readOnlyHint=true, but the description says it 'hangs up an active voice call' and 'terminates' a call, which is an action that changes the environment/state of the call. This conflicts with a read-only declaration. (idempotentHint/idempotency and destructiveHint=false are consistent and add no contradiction.)

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 tight sentences, front-loaded with the action and identifier, followed by usage and the idempotency guarantee. No filler; every sentence earns its place.

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 action tool with full schema coverage and no output schema, the description covers purpose, usage, and idempotency. However, side effects (e.g., whether the callee is notified, permission/auth needs) are absent, and the description is silent on behavioral impact that is muddled by the readOnly annotation.

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 call_id, reason, and in_workspace are already fully documented with examples. The description only restates call_id as the key and implies the post-calls.make source, adding little beyond the schema; baseline 3 applies.

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?

Specific verb + resource + identifier: 'Hang up an active voice call by call_id.' This clearly distinguishes it from sibling call-control tools like calls_transfer, calls_mute_translation_tts, and calls_make.

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 clear triggering context: use after calls.make to terminate before the callee does, or to abort a stuck call. It references a sibling (calls.make) as the prerequisite but does not name explicit alternatives/exclusions (e.g., transfer vs. hangup) or state when NOT to use it.

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