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

With no annotations, the description carries the full burden and largely does so: it discloses cost ($0.001 per call via x402/USDC on Base), the payment requirement, and that responses carry a provenance chain and Ed25519 attestation. It omits failure/error behavior (e.g., unknown area id) and any rate-limit or retry guidance, which keeps it short of 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?

Two front-loaded sentences with no filler: the first establishes purpose and scope, the second covers cost and response guarantees. The second sentence is a dense run-on, but every clause (price, payment rail, provenance, attestation) earns its place.

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?

With no output schema and no annotations, the description does cover pricing, payment, and response integrity, but leaves the critical input side under-specified — no id format, no way to find a valid id, no error behavior for a tool whose sole required parameter is an identifier.

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 50% — payment is documented (including the free-quote case) but 'id' has no description, only maxLength 40. The description hints that id identifies 'one metro or county area' but never states the expected code format (FMR area code vs. county FIPS), so it only partially compensates for the gap.

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+resource: HUD Fair Market Rent, scoped to 'one metro or county area,' with rent broken out by bedroom count for the current fiscal year. The 'one area' scoping implicitly separates it from the sibling fmr_area_search, though it does not name that sibling explicitly.

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?

There is no when-to-use or when-not-to-use guidance. The obvious alternative, fmr_area_search, is never mentioned, so an agent has no stated path to obtain or disambiguate the required 'id' before calling lookup rather than search.

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