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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false. The description adds a critical behavioral fact: each call costs 0.05 USDC, and data starts on 2026-09-14. It does not mention pagination or response shape, but the annotation coverage lowers the burden.

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?

The description is two compact clauses with no redundant wording. The cost warning is front-loaded, and the data scope is stated efficiently.

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 simple read-only history tool, the description plus schema covers cost, ticker, date format, and data start. However, it does not explain what a 'fixing' contains, how this differs from tokens_fixing, or what the return payload looks like, and there is no output schema to compensate.

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%, with all parameters documented including date formats and a ticker example. The description adds no parameter-specific semantics beyond the general 'daily fixings' context, so the baseline of 3 is appropriate.

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 identifies the resource (token ticker), the data type (daily fixings), and the temporal scope (from first snapshot 2026-09-14). It is clear enough, though it does not explicitly distinguish itself from the sibling tokens_fixing tool.

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?

No guidance is given on when to use this tool versus tokens_fixing, tokens_board, or tokens_quotes. The description mentions cost and data availability, but provides no exclusions, alternatives, or selection criteria.

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