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

Annotations already cover safety (readOnly, idempotent, closed-world), so the description's job is narrower; it adds genuine context by defining the blended index formula, the currency/unit basis, and the three change horizons returned. It does not discuss ordering, staleness, or coverage of the company list, but for a read-only snapshot tool this is solid added value.

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, zero filler, and the core metric definition is front-loaded before the optional-parameter behavior. Nothing could be cut without losing information.

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 single optional-parameter read-only tool with no output schema, the description supplies the metric definition, units, time windows, and what changes when a company is specified — everything an agent needs to call it and interpret the result.

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% and the enum already documents the accepted companies, so the baseline is 3; the description earns an extra point by explaining the semantic consequence of passing a company (response expands to per-model usage shares and posted prices) rather than just repeating the field.

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+resource ('Latest token price index per AI company') and pins down the metric's definition (USD per 1M tokens, 3:1 input/output blend) plus the change windows returned. It does not explicitly name the sibling tools (get_gpu_prices, get_price_history), but 'Latest' implicitly separates it from a history endpoint.

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?

'Give one company to also get its models' usage shares and posted prices' clearly explains the conditional benefit of supplying the optional parameter versus omitting it for the full list. No explicit exclusions against get_price_history are given, so it stops short of a 5.

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