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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorld, so the safety profile is covered. The description adds genuinely new behavioral context: the credit cost of one per call and the exact sequence convention. It stops short of saying what the return shape is (list vs string), which is the main remaining gap.

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?

A single front-loaded sentence with the core behavior first and the cost note parenthesized at the end. Nothing is redundant or padded.

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 one-parameter, side-effect-free computation tool with full schema coverage and no output schema, the description gives everything needed to invoke it correctly. The only soft spot is not describing the returned value's shape, which is minor for such a predictable output.

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% and the parameter documents 'number of Fibonacci numbers to generate (must be positive)', so the schema carries the semantics. The description restates 'first n numbers' but adds no format, upper-bound, or type clarification, leaving the schema's string-typed 'n' described as an integer unaddressed. 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 names a specific verb ('Generates') and resource ('the first n numbers in the Fibonacci sequence') and pins down the exact sequence convention (each number is the sum of the two preceding, starting 0 and 1). An agent can distinguish it from neighbours like factorial or is_prime without opening the schema.

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?

Usage is implied by the definition rather than stated: an agent can infer it should call this when it needs Fibonacci numbers. There is no explicit when-to-use, no when-not-to-use, and no mention of the sibling math tools (factorial, least_common_multiple) it could be confused with.

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