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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world). The description adds genuinely useful context beyond them: the 0.10 USDC per-call cost, which is critical for an agent deciding whether to invoke, plus the daily snapshot scope and frontier basket inclusion.

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 tightly packed sentences with no wasted words, and the cost is front-loaded so an agent sees the paid nature immediately. The phrasing is terse to the point of being cryptic ('blended fixing', 'frontier basket').

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 annotations carrying the safety profile and an output schema present, the description only needs to convey scope and cost, which it does. The main gap is lack of routing against the numerous sibling tokens_* tools, but nothing essential to invocation is missing.

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 single optional 'day' parameter already documents the YYYY-MM-DD format and default. The description's 'for one day' reinforces the semantics but adds no format or edge-case detail beyond the schema, so the baseline 3 applies.

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 resource ('Every model's input, output and blended fixing for one day, plus the frontier basket') with an implicit fetch verb. It is distinguishable from tokens_history (time series) via the 'for one day' scope, though the terms 'blended fixing' and 'frontier basket' are jargon-heavy and the sibling tokens_fixing is not explicitly contrasted.

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?

There is no explicit when-to-use guidance and no alternatives named among the many tokens_* siblings (tokens_fixing, tokens_history, tokens_models, tokens_quotes). The scope 'for one day' weakly implies a daily snapshot rather than history, but the agent must infer this.

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