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

The description discloses the side effects (creates a key), the limits (at most 3 per IP per day, 10,000 weighted units per day, 5 requests/s), the return structure (key shown once, key_prefix, door, fences, doorways, terms, skill), and that no key is needed. Since annotations provide no hints (all false), the description carries the full burden and does so thoroughly.

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 well-structured and efficient. It opens with the core purpose and the key limits, then flows into usage guidance, exclusions, return format, and creation limit. Every sentence adds unique value, with no fluff or redundancy.

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?

Given the absence of an output schema and empty annotations, the description must independently provide all necessary context for an agent to call the tool correctly. It covers the purpose, when to use it, what it returns, the limits, and the lack of required authentication. This is fully complete for a tool with no parameters.

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 tool has zero parameters, so the schema provides no parameter semantics (100% coverage vacuously). The baseline for 0 parameters is 4. The description does not need to explain parameters, and it doesn't; it appropriately focuses on behavior and output. No additional parameter information is necessary.

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 clearly states the verb 'Get' and the resource 'a FlexYield API key with no signup'. It explicitly distinguishes itself from siblings by stating it is for when you have no key yet, and points to what_can_i_do and list_plans as alternatives for other cases. This provides strong differentiation.

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?

Explicit usage guidance is given: 'Use it once, when you have no key yet; then send the key as the bearer on every other call.' It also states what it is NOT for ('Not for a key you already hold' and 'not for a human's paid plan') and names the alternative tools to use instead, leaving no ambiguity.

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