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

Annotations already cover read-only/idempotent/non-destructive, and the description adds real context beyond them: the result shape (TOTAL first, then grouped breakdown), the data freshness model (periodic snapshot with `data_as_of`), the keyless auth profile, and a failure mode (unfiltered queries cannot be answered accurately). It stops short of covering pagination semantics for large groupings or what an over-limit result looks like.

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?

Purpose is front-loaded in the first sentence and the description follows a readable order: what it returns, constraints, when to use, when not to use, freshness. It runs long and the parenthetical about pre-1992 fiscal years is a minor tangent, but almost every clause carries usable information.

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 an 8-parameter aggregation tool with no output schema, the description supplies the missing return structure (total plus grouped breakdown), the mandatory filter rule, the default grouping behavior, and freshness semantics. An agent has everything needed to call it correctly and interpret the response.

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%, so every one of the 8 parameters is already documented, including the conditional requirement that has been folded into each of the fiscal_year and district_or_circuit descriptions. The description restates that constraint but adds no syntax, code vocabulary, or format detail beyond the schema, which is the expected baseline-3 outcome.

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 (aggregate) and resource (FJC IDB federal caseload statistics) plus the dimensions available (nature of suit, offense code, disposition, fiscal year, district/circuit). It also explicitly contrasts itself with the sibling fjc_case_outcome_lookup, so an agent can route between the two without opening schemas.

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?

Gives an explicit use case in the caller's own phrasing ("how many X cases were filed/terminated in district Y in year Z") and names the alternative tool plus the condition that selects it (single case's outcome). It also states a hard invocation constraint: requires fiscal_year AND/OR district_or_circuit.

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