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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive behavior. The description adds that data is published monthly and requires no authentication, and it lists the security types returned, which is useful beyond the annotations.

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 description is compact, front-loaded with the core purpose, and each sentence adds value: purpose, security types, filter guidance, and source/auth. No redundancy or unnecessary detail.

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 read-only tool with an output schema and rich annotations, the description covers the essential context: what it returns, how to filter, default behavior, source, and auth requirements. Nothing critical is missing for an agent to invoke 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% with both limit and security_type well documented. The description adds the practical hint 'Use limit=15 for the latest monthly snapshot' and explains the security_type filter values, enhancing the schema's semantics.

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?

The description clearly states the verb 'Get' and resource 'average interest rates on outstanding US Treasury securities', and explicitly lists the security types covered, distinguishing it from sibling tools like treasuryfiscal.debt.current or treasuryfiscal.yield.quarterly which cover different datasets.

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?

It provides usage tips like 'Use limit=15 for the latest monthly snapshot' and explains filtering by security_type, but it does not explicitly state when not to use this tool or compare with alternatives. The context is clear enough that an agent can infer this is for average interest rates, but it lacks explicit exclusions.

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