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

Beyond annotations (read-only, idempotent, non-destructive), the description discloses pricing, an alternate HTTPS endpoint, the valid input range, and the rule that non-fibbinary inputs return 0. That is useful context for a paid API call, though rate limits or latency are not mentioned.

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 core definition is front-loaded, followed by examples that directly illustrate behavior, then practical call details (range, price, URL). Every sentence has a purpose, though the pricing and endpoint sentences are slightly tangential to the mathematical operation.

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 deterministic function with one parameter and no output schema, the description is sufficiently complete: it states the return value semantics, gives examples, and adds pricing/endpoint details. Nothing critical for an agent to call it correctly 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 0%, so the description must carry parameter meaning. It explains that n is the number to locate and gives concrete input-output examples (0→1, 1→2, 5→5, 10→8, 16→9, 3→0), which add substantial clarity. The range restates the schema's min/max, but the examples are valuable.

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 (position/index) and resource (among fibbinary numbers), making the inverse mapping clear. Examples reinforce the meaning. It does not explicitly differentiate from siblings like fibbinary_nth or fibbinary, but the operation is unambiguous.

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 definition implies usage (find the index of a fibbinary number, returning 0 otherwise) but never names when to use this versus alternatives such as fibbinary, fibbinary_next, or fibbinary_nth. Guidance is inferable but not stated.

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