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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered. The description adds some behavior (substring matching applies only to state) but says nothing about return format or match ranking, so it adds modest value on top of the structured data.

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?

Two tight sentences with zero waste; the core action is front-loaded and the usage routing comes second. Every clause earns its place.

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 simple, annotation-covered lookup with no output schema, the description is nearly sufficient: it conveys what is returned (FIPS codes) and how to supply input. The only gap is lack of detail on output shape, which is minor given the tool's narrow scope.

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 the schema already documents query, level, and limit. The description restates the accepted query formats (state name, 2-letter code, 5-digit ZIP) and adds that substring matching is state-only, which is marginal beyond what the schema already conveys.

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 and resource ('Look up Census FIPS codes by name') and clearly positions itself against the many census_* data siblings by framing itself as the code-resolution prerequisite. An agent can tell what it does and where it sits in the family without opening the 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?

Explicitly says when to reach for it: 'Use this to find the FIPS codes needed by other census_* tools,' which gives a clear call condition and dependency role. It stops short of naming exclusions or when-not-to-use, but the intended context is unambiguous.

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