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

Annotations only declare readOnlyHint and openWorldHint; the description adds substantial context the annotations cannot carry: the x402 pricing ($0.002 USDC/call), that failed calls are free, the quote-then-sign payment flow, the 3 free calls/day allowance, and that a non-match is refused free. This is exactly the extra behavioral detail an agent needs before paying.

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?

Well front-loaded: purpose first, then cost, then when-to-use, alternative, parameters, and returns. However, the opening sentence already enumerates the full return field list (address, ZIP, county, FIPS, state, census tract) and the trailing 'Returns:' line repeats it verbatim, which is wasted text.

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 two-parameter, no-output-schema geocoder with light annotations, the description covers the purpose, the exact return fields, payment/quote mechanics, cost, input constraint, and failure handling. 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 baseline is 3, but the description adds a meaningful constraint beyond the schema ('US street addresses only (with a house number)') and ties `payment` to the quote workflow. It stops short of full added value but meaningfully supplements the schema.

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 and resource ('Turn a US street address into latitude and longitude') and enumerates the exact outputs plus the data source (US Census Bureau geocoder). It explicitly scopes to US street addresses with a house number, and names a sibling alternative, so an agent can distinguish it from weather_forecast without opening either schema.

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?

Contains an explicit 'When to use' line and a 'Use instead' line routing to weather_forecast when only weather is needed. The payment precondition (call without `payment` to get a quote) is also spelled out, leaving nothing to inference.

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