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

Annotations already declare read-only, idempotent, closed-world, non-destructive, so the safety profile is covered. The description adds genuine behavioral context beyond that: the 2025 vintage, the LEI grouping key, the per-filer jurisdiction count, the universe totals and the top-25 concentration share. It stops short of stating ordering guarantees when `limit` < 50 or any freshness/caveat notes.

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?

The core computation is front-loaded in the first sentence and the payload contents are enumerated efficiently. The trailing fragment 'A national aggregate.' repeats what the first sentence already established, and the reference-URL sentence is of marginal operational value, but neither is costly.

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-optional-parameter read tool with no output schema, the description does the important work of enumerating what each row contains and what the aggregate totals are, which is exactly what a caller needs. The only gap is not explaining how `limit` affects the returned ranking or what the ordering is by default.

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 `limit` parameter is fully documented in the schema (1–50, default 25), so the schema does the work. The description adds nothing about how the limit interacts with the ranking — e.g. whether it truncates the top-N list — so it neither helps nor hurts beyond baseline.

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+resource+scope: 'Every HMDA filer across the 50 states and DC grouped by LEI and ranked by 2025 investor-property loan count'. It also names the aggregation shape (national/cross-state) and the computed fields, which is what separates it from the sibling investor_lenders_by_state.

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?

'A national aggregate' and the title's 'cross-state' imply this is the nationwide roll-up, so an agent can infer it is the wrong pick for a single-state question. However, it never explicitly routes the caller to investor_national_alternatives or says 'use investor_lenders_by_state when you need one state', so the guidance stays implicit.

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