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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, but the description adds meaningful behavioral context beyond them: it is read-only, requires no key, returns a JSON object with specific fields, and handles unknown codes by returning known=false with a hint. This fully discloses the tool's behavior and edge case without contradicting 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?

The description is three sentences and every sentence earns its place: what it does, when to use it, what it returns, and what it is not for. The key information is front-loaded, and there is no filler or repetition of the tool name.

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 single-parameter, read-only tool with no output schema, the description is fully complete. It explains the return shape (code, http, title, meaning, steps, doorway, decoder), the unknown-code case, auth requirement (no key needed), and usage exclusions. Nothing an agent needs to invoke 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 description coverage is 100%, so the schema already documents that the only parameter is an integer JSON-RPC error code such as -32007. The description reinforces this with an example and context, but does not add substantial meaning beyond the schema — so the baseline of 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 states a specific verb ('Explain'), a specific resource ('a FlexYield error code'), and precisely what the tool provides: meaning, steps, and doorway. It also names what it is not for (upstream chain errors, filing tickets) and explicitly routes ticket filing to manage_tickets, distinguishing it from siblings without opening schemas.

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 description gives an explicit trigger: use it whenever a call returns an error code you do not know, before retrying or filing a ticket. It also provides clear exclusions and alternatives: not for upstream chain errors that are not ours, and not for filing the problem — for that use manage_tickets with the request_id.

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