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

With readOnly/idempotent annotations already covering safety, the description adds real substance: it discloses the return payload (annual rate bps, upfront rate, matched cell, rule id with effective date and sha256, quotable sentence) and the failure mode (CONDITION_MISSING block, no number). This is exactly the behavioral context annotations do not carry.

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?

Dense but front-loaded: ANSWERS, PARAMS, then NOT FOR. Every sentence earns its place; the eleven-cell rationale justifies the no-guess behavior in one clause.

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?

No output schema, yet the description fully specifies return fields and the error shape. For a four-param, zero-required lookup with an unconventional failure mode, the definition gives the agent everything needed to call it and interpret the result.

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 the baseline is 3, but the description adds semantics the schema lacks: ltv_pct as 'e.g. 96.5', base_loan_amount as before upfront MIP financed, term_years, and the date format. It names each parameter and clarifies that a missing one triggers the CONDITION_MISSING path, which is beyond 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 (resolve) and resource (the FHA annual MIP cell) and front-loads a natural-language example of the exact question it answers. Clearly distinguishable from siblings like get_rule or get_national_fha_stats.

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?

Explicit 'NOT FOR' clause excludes pre-2023-03-20 cases, HECM/reverse, Title I, and payment figures. Adds a behavioral rule: if a parameter is missing it returns CONDITION_MISSING rather than guessing, and explains why (eleven cells, a guess is wrong more often than right).

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