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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description is not obligated to restate them. It does add genuinely useful behavioral context by disclosing what the response contains: the long-context rate and any announced price change. It does not mention behavior for unknown model ids or staleness of 'current', which keeps it off a 5.

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?

One sentence with zero filler, front-loaded with the core purpose and followed by the return-content detail. Nothing is redundant with the title or the schema.

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 one-parameter lookup with no output schema, the description covers purpose, example inputs, and the shape of the returned data, which is what an agent needs to call it correctly. The remaining gap is error behavior on invalid ids and whether the price is per-token or per-unit.

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% for the single 'model' parameter, so the baseline is 3. The description adds concrete example ids ('gpt-4o-mini', 'claude-sonnet-4-5') that help an agent form a valid value, but it says nothing about id format rules or what happens with an unrecognized id.

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 states a specific verb and resource ('Current list price of one model by id') and scopes it to a single model, which implicitly separates it from a bulk-listing sibling. It stops short of naming the alternative (e.g. list_llm_prices), so the differentiation is inferred rather than stated.

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 only implied: an agent can infer you call this when you already know one model id and want its rate. There is no explicit when-to-use or when-not-to-use guidance relative to estimate_llm_cost, compare_llm_costs, or list_llm_prices, and no prerequisites are mentioned.

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