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

Beyond the annotations' destructive/openWorld flags, it discloses the real-world consequences an agent cannot infer: a real paid call will be placed, limits of 3 callbacks per call within 14 days, a minimum 2-minute and maximum 14-day lead time, no calling-hours window, and a named failure mode 'callbacks_disabled'. It also names cancel_call as the reversal path, which is exactly the context destructiveHint alone does not supply.

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?

Purpose is front-loaded, then compliance, then routing to siblings, then limits — a sensible priority order with no filler. The compliance sentence is dense but all of it is load-bearing; a small trim of the overlapping time-window statements (repeated in the compliance and limits sentences) would tighten it.

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 destructive, open-world scheduling mutation with only two parameters, the description covers preconditions, limits, cost, failure mode, and reversal. The output schema handles the returned scheduled time, which the description points at without duplicating.

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%, including the ISO 8601 format and the Europe/Paris default, so the description need not restate syntax. It still adds binding constraints on callback_at that the schema lacks ('at least 2 minutes from now', 'at most 14 days ahead') and clarifies that the number and task are inherited from call_id rather than passed. Slightly redundant on 'the time is kept as given'.

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 and resource ('Schedule a new attempt of a finished call (same number, same task)') and immediately distinguishes the two nearest siblings: get_call as a precondition and place_phone_call for a different number or task. An agent can pick it out of the sibling list without opening any schema.

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 an explicit precondition ('only after get_call shows done=true'), an explicit alternative ('To call another number or do a different task, use place_phone_call'), and a compliance gate ('only on the user's request'), plus the closing instruction to use cancel_call to undo. When-to-use and when-not-to-use are both covered.

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