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

Annotations already cover read-only and open-world traits, and the description adds genuinely new context: results are aggregated with no borrower data, pricing is $0.002 USDC per successful call via x402 on specific chains, and failed calls are not charged. That payment/billing behavior is exactly what an agent needs and cannot get from 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?

Information is front-loaded: data source and aggregation first, then the filter default, then pricing. Two dense sentences with no filler, though the pricing clause is long enough to slightly blur the read.

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 an output schema present, return values need not be explained, and the description covers aggregation level, filter default, and cost model. The only minor gap is not stating whether multi-year ranges or all-states queries are supported, though the required state/year params imply single-scope calls.

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 coverage is 100%, so all three parameters (year, state, actionTaken) are already documented, including the actionTaken default of 1. The description only restates the default and the aggregation semantics, adding little beyond the schema, so baseline 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?

States a specific verb and resource: 'Official US mortgage application totals from the CFPB HMDA Data Browser API', scoped to one state and year, returning loan counts and total dollar amount. This clearly separates it from listing/rate siblings like realestate_bankrate_mortgage_rates or realestate_zillow.

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 scope (one state + year, aggregated) and the actionTaken filter with its default imply when the tool applies, but there is no explicit 'use this instead of X' routing against similarly named siblings, and no prerequisites or exclusions are stated.

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