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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the bar is lower, and the description still adds meaningful behavior: the score range, that the response includes a factor breakdown and methodology link, and the non-obvious 'not found' condition for lenders without a published Score. It does not state the error shape or whether a missing lender returns an empty result versus an error, but the added context is substantive.

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 dense sentences with zero filler; the identity of the resource and its scope come first, and the failure condition is placed last as a caveat. Every clause carries information an agent needs.

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 lookup with no output schema, the description covers what the value is, its range, the key used, the response contents (factor breakdown, methodology link), and the not-found case. The only real gap is the absence of any pointer to the sibling tool that lists lenders, which would help an agent choose correctly.

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% and there is only one parameter, so the schema already documents 'Company NMLS id' completely; the description's 'by company NMLS id' merely restates it. No format, validation, or lookup nuance is added beyond what the schema provides, 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 names a specific resource (the FreeRateUpdate Score for a lender, keyed by NMLS id) and scopes it with qualifiers ('verified, currently in-network', 0-100 range), which is far more specific than a restatement of the name. It never references the sibling get_lender_universe, so an agent must infer the distinction from the names alone rather than from explicit differentiation.

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?

Usage context is implied by the eligibility qualifiers ('verified, currently in-network') and the failure condition 'Companies without a published current Score are not found' tells the agent when the lookup will yield nothing. However, it gives no guidance on when to prefer this tool over get_lender_universe or the other rate/value siblings, and no prerequisites are stated.

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