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

Annotations already declare readOnlyHint=false, destructiveHint=true, and idempotentHint=false, covering the core safety profile. The description adds the 'in-progress' state requirement, which is useful, but it does not explain what happens if the call is already ended or a non-active call id is supplied.

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 sentence contains the action, the target state, and the locating mechanism, and all content is relevant. There is no redundant filler or boilerplate.

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, one-parameter mutation with a rich set of annotations, the description is nearly complete at the required level of detail. The only minor gap is the lack of behavioral details for already-terminal state or error handling, but this is partially covered by the 'in-progress' qualifier.

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% with the call_id description 'Call id of an active call,' so the schema fully documents the parameter. The description's 'by id' adds no additional semantics beyond what the schema already provides.

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 a specific verb ('hang up'), a resource ('in-progress call'), and the lookup key ('by id'). This differentiates it from siblings like place_call, get_call, and list_calls without needing to inspect schemas.

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?

'Hang up an in-progress call by id' gives clear context: this tool applies to active calls only, not to scheduled or completed calls. It does not explicitly name alternatives or exclusions, but the intended trigger state is obvious and sufficient for this simple action.

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