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

Beyond the annotations it discloses a lot: a pre-send refusal policy for prohibited answers, the ~45 second timing window, the one-minute hold extension requiring callee consent, callback retention behavior, and the wrong_call_state failure mode. What it leaves implicit is the irreversibility implied by destructiveHint=true — that a spoken answer cannot be retracted — and there is mild tension with idempotentHint=false when it says re-sending the same answer after a callback is harmless, though that claim is scoped to the ended-call case.

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?

The core action and the usage gate are front-loaded in the opening two sentences, and every subsequent sentence carries operational content (compliance, secrets, timing, hold, callback, error). It is dense and long for a three-parameter tool, with the compliance clause folded into the first sentence rather than separated, which slightly hurts scanability.

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 no explanation, and the description covers the remaining risk surface: preconditions, refusal policy, sensitive-data handling, timing pressure, escalation paths, and the post-call state. An agent has everything needed to decide whether to call and how to phrase the answer.

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 already 100%, yet the description adds real semantics: the answer must be the user's actual information or decision rather than invented content, must not ask the callee for codes or card details, and can encode sensitive values as [secret: value] so transcripts mask them. It also ties question_id to pending_question.question_id from get_call, which is behaviourally more informative than the schema's 'omit to answer the question currently pending'.

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 first sentence states a specific verb and resource — send the user's answer to a pending question and return confirmation of relay — and anchors it to a concrete signal ('pending_question' from get_call). This makes it immediately distinguishable from hold_call_question, transfer_call_to_user, cancel_call, and get_call.

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 states the enabling condition ('Use it only when get_call shows a pending_question'), then routes to alternatives by situation: ask the human and use hold_call_question if time is short, or transfer_call_to_user if the callee wants to speak to the user. It also names the terminal follow-up ('Then continue with get_call') and clarifies the callback-after-end case where the tool still applies.

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