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

Annotations only declare readOnlyHint, so the description carries the behavioral burden and does so richly: DATA_UNAVAILABLE refusal on an unreachable store, partial-FY semantics, result ordering (newest FY first / largest first), the curated-crosswalk caveat, and that it is free/public-domain. This is substantially more than annotations provide.

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 and front-loaded, with the two-shape rule stated early and caveats clustered afterward. It is long, and some constraint detail duplicates the schema, but nearly every sentence carries operational value and nothing is buried.

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?

Despite no output schema, the description explains both return shapes (per-FY obligations with dropped_unresolved, and the leaderboard), ordering, defaults, and failure modes, so an agent has everything needed to call it 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 coverage is 100%, so the baseline is 3, but the description adds genuine meaning beyond the schema: mutual exclusivity of ticker/fiscal_year, sort ordering of the two result shapes, and the leaderboard scope ('not of all federal contractors'). These clarify usage beyond the parameter descriptions.

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 (federal-contract obligation history / fiscal-year leaderboard) and is explicitly different from any sibling by naming its two output shapes and its USAspending source. An agent can tell exactly what this returns versus get_fundamentals or ol_operating_kpis without opening a schema.

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 explicit when-to-use for each mode: pass `ticker` for per-year history, `fiscal_year` for the leaderboard, and both is refused. It also warns not to compare a partial (period_complete false) year to a full one and clarifies obligations are not company-reported revenue.

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