Listen (on a call)

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

Beyond the annotations, it discloses the key behaviors: it returns immediately if data is pending, otherwise blocks up to wait_seconds (default and maximum 40), emits the literal sentinel string '(still on the call, nothing said)', and reaches a terminal state after the call ends. This explains the non-idempotent, state-advancing nature implied by readOnlyHint=false and idempotentHint=false.

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 short sentences, front-loaded with the situational trigger ('During a call'), followed by behavior, sentinel interpretation, and the terminal rule. No filler, and each sentence carries distinct operational information.

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?

With one optional parameter and no output schema, the description covers everything an agent needs: return semantics, blocking/timeout behavior, the exact sentinel string, and when to stop calling. Return values are described in prose, compensating for the absent output schema.

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% and the single parameter is fully documented there, so the baseline is 3. The description adds meaning beyond the schema by explaining the conditional behavior: the wait only happens if nothing is already waiting, making wait_seconds a maximum blocking time rather than a fixed sleep.

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 opens with a precise verb+resource and scope: 'During a call: return what the user has said since you last heard from them.' The delta semantics ('since you last heard from them') distinguish it from a full transcript read and implicitly from the sibling 'say'/'speak_and_listen' tools, which produce speech rather than consume it.

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?

It gives explicit lifecycle guidance: call it again to keep waiting when the sentinel '(still on the call, nothing said)' is returned, and stop calling once the call-ended signal appears. What's missing is an explicit statement of when to prefer this over 'speak_and_listen' or 'say', so it stops short of full alternative routing.

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