check_availability

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

Annotations only declare readOnlyHint and openWorldHint=false; the description adds substantial context beyond that: the three possible outcomes (available/partial/unavailable), the partial-volume and viewable-share fields, the fallback alternatives, and critically that figures are forecast estimates rounded down, not reservations. That last point prevents an agent from treating the result as a booking.

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 tight sentences, front-loaded with the core action and then the return semantics. Every clause earns its place; nothing is redundant with the name 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?

With no output schema, the description carries the full burden of describing the return value, and it does so thoroughly: outcome states, partial volume, viewable share, alternative periods/families, and the estimate-not-reservation caveat.

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%, so the schema already documents all five parameters (token, period, family_id, impressions, client_request_id). The description only hints at a rounding default ('2 significant figures by default'), which does not add parameter-level syntax beyond the schema. Baseline 3.

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 with scope: checks whether the publisher can deliver N impressions of a product family in a period. This is clearly distinguishable from siblings like get_forecast (retrieves forecasts) and create_intent (commits a buy).

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 (a pre-commit availability probe before create_intent) but never stated explicitly, and no sibling alternative or when-not condition is named. The agent must infer the place in the workflow from the sibling list.

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