Cancel call

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

Goes well beyond the annotations: it discloses the intermediate cancel_pending state pending ops confirmation, the refund behavior for a confirm before dialing, the specific cancel_too_late error when the dial already started, and the billing/VA-payment consequence of a dial after a confirmed cancel. None of this is derivable from destructiveHint/idempotentHint/openWorldHint.

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?

Five short sentences, front-loaded with the action, then packed with state, refund, error, and billing facts. No filler sentences and no repetition of the title or annotations.

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?

An output schema exists so return values need not be described, and the description covers lifecycle states, the failure mode, and financial consequences thoroughly. Minor gap: no mention of permissions/ownership or who may cancel, which for a destructive operation would be useful context.

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?

There is one required parameter (call_id) with 0% schema description coverage, and the description never mentions it. The parameter is largely self-evident from the name, but the description adds no meaning (format, whether it is a UUID, whether the call must be in a particular state).

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+resource ('Cancel a call') and immediately elaborates the state the call lands in, so the agent knows exactly what operation this is. It does not explicitly contrast itself with the call-vs-task siblings (cancel_task, confirm_task), but the resource is unambiguous from the name and first sentence.

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 implied rather than routed: the description explains what happens depending on call state (pre-dial refund, dial-started failure), which helps the agent predict outcomes, but it never names an alternative tool or states prerequisite conditions for choosing this over cancel_task or update_call.

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