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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: the result is non-binding and the actual rate is determined at fill time, which is important for an agent deciding whether to treat the output as final.

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 with no filler. The core purpose is front-loaded, and the critical caveat about non-binding rates is placed in the second sentence where it naturally reinforces the estimate nature without burying the main point.

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 read-only estimate tool with fully documented parameters, the description is nearly complete. It explains the rate mechanism, the estimate's non-binding nature, and when the final rate resolves. It does not explicitly state the response shape, but no output schema exists and the title plus purpose make the expected result clear enough.

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%, so the baseline is 3. The description confirms the domain (Base USDC and fiat) but adds no additional meaning about the amount format, currency semantics, or optional platform parameter beyond what the schema already provides.

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 ('Estimate'), resource ('fiat received for Base USDC'), and rate source ('live Chainlink oracle rate'). Explicitly contrasts itself with a locked quote, which distinguishes it from quote-like sibling tools without needing to open their schemas.

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 provides clear context on when to use the tool: to get an estimate at the live oracle rate. The explicit 'not a locked quote' exclusion and the note that the binding rate resolves when a buyer fills give useful guidance, though it does not name a specific alternative tool like peer_quote.

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