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

With all annotations false, the description carries the full burden. It adds meaningful behavior: instant issuance, no human/signup/card, one-off trial credit, free/never metered, and email optional with a key always issued. Minor inconsistency with schema's 'Improves the chance' vs description's 'only affects whether' prevents a 5.

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 sentences, front-loaded with purpose, and every sentence adds value. The 'CALL THIS FIRST' emphasis is clear and efficient. 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?

The tool is simple, with one optional parameter and an output schema. The description covers when to call, what it returns (a key with trial credit), free usage, email semantics, and the retry pattern. Given the output schema exists, no need to detail return values. The description is complete for this tool's context.

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 schema already covers the email parameter 100% (optional, improves chance of trial credit). The description repeats this and adds 'only affects whether', which slightly contradicts the schema's 'improves the chance'. Since schema coverage is high, baseline 3 is appropriate, and no additional parameter meaning is added.

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 tool's purpose: 'Get a FactReason API key for yourself' with specific details about instant issuance, no signup, and no card. It distinguishes itself from sibling tools by focusing on key creation rather than API discovery, schema, or auth playbooks.

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 provided: 'CALL THIS FIRST if you have no key, or as soon as any FactReason tool returns HTTP 402 Payment Required — then retry the original call with the key.' It also notes the tool is free and never metered, reinforcing when it is appropriate to use.

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