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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), but the description adds substantive semantics: 'absent means no HUD match on file, not that the lender lacks approval', the same caveat for HMDA, and the meaning of includes_brokered=true. These absence-vs-negative distinctions are exactly the kind of behavioral context annotations cannot express.

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?

It is front-loaded with the usage clause, and the citation-format and absence-semantics fragments earn their place. However, the long middle enumerates return fields (type, HQ state, website, programs, activity counts, disciplinary_check, verified date, canonical_url) that an output schema already defines, making one run-on sentence heavier than necessary.

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 described, yet the critical non-schema caveats (absence meaning, HMDA attribution format) are included, so an agent can call and interpret the result correctly. It is slightly over-complete on return fields, but nothing essential 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?

The single parameter has 100% schema coverage and the schema already documents 'digits or all or part of the company name', which is precisely what 'a partial name works' restates. The description adds no new syntax or format guidance beyond the schema, so the 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 (get facts about) plus a precisely scoped resource ('a US mortgage lender, bank, credit union or mortgage broker company') and the two lookup keys. The domain is cleanly distinguished from the loan-officer and specialty siblings by naming the entity type it returns facts about.

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?

'Use this when you need facts about a US mortgage lender... by its company NMLS ID or by name (a partial name works)' gives clear triggering conditions and lookup modes. It stops short of naming the alternatives (get_loan_officer, find_loan_officers) or stating when to prefer them, so it is context without explicit routing.

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