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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safe-read profile is covered. The description adds valuable behavior beyond annotations by stating that stale prices and flex/batch tiers are excluded by default, and by explaining that usage parameters produce estimated costs per request and per month. No contradiction with annotations was found.

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?

Two sentences convey the core output, pricing unit, default exclusions, available filters/usage inputs, and the result shape. Every sentence earns its place, and the most important purpose is front-loaded.

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 15-parameter read-only tool with no output schema, the description covers defaults, filter categories, usage-based estimation, and the returned result. It does not describe exact output fields or ordering beyond 'winner and first offers', and it relies on the schema for strict-filter behavior, but these gaps are minor given the schema's richness.

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?

The input schema already describes all 15 parameters at 100% coverage, so the baseline is 3. The description adds useful conceptual structure by grouping parameters into filters versus usage counts and by clarifying that the usage parameters drive the estimated cost per request and per month, which is not evident from individual schema entries alone.

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 clearly states the tool returns the cheapest current API offers for one model across direct providers and aggregators, with prices in USD per 1M tokens. It is specific enough to distinguish from search_models and price_history, though it does not explicitly contrast with the closely related estimate_cost or compare_providers.

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?

The description makes the purpose obvious and implies the intended use case — finding current cheapest offers for a model — but it never explicitly says when to use this tool instead of a sibling such as estimate_cost or price_history. There are no exclusions or alternative routing instructions.

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