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

Annotations already cover read-only, idempotent, open-world, and non-destructive behavior. The description adds meaningful extras: the $0.001 USDC cost per call and the byte-identical HTTP equivalent, which helps an agent understand exact behavior and side effects beyond the annotations.

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?

Three tightly written sentences: the first states the core purpose, the second gives the motivating use case, and the third adds cost and an exact endpoint equivalent. No filler or repetition.

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, optional-parameter lookup with an output schema and rich annotations, the description is complete. It covers what the tool returns, how filtering works, the use case, cost, and the underlying HTTP contract, leaving no practical gap for correct invocation.

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?

The input schema already describes both parameters with 100% coverage, establishing a baseline of 3. The description adds value by explaining 'contains' as a case-insensitive substring filter on the pair id and by showing the HTTP query form 'contains=USD&limit=20', which reinforces parameter semantics.

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 action and resource: it returns the pair ids Bitfinex publishes for its spot exchange, optionally filtered by substring. It clearly distinguishes this from sibling market_bfex_candles and market_bfex_ticker by focusing on the list of tradeable pair ids.

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 phrase 'the lookup that stops a bot guessing a market that does not exist' gives a clear use case: validate pair existence before trading. It does not explicitly name alternatives or exclusions, so it falls short of a full 5, but the context is strong.

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