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

Annotations already cover read-only, open-world, idempotent, and non-destructive behavior. The description adds useful behavioral context about aligning on business dates and what the response includes (both canonical series, component values, percentage-point and basis-point spreads, pagination, provenance, hosted coverage), though it omits auth, rate limits, or error behavior.

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?

Four sentences, front-loaded with the core operation, followed by use cases, alias acceptance, and a scope disclaimer. Every sentence adds distinct value with no redundancy.

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?

No output schema exists, so the description carries the return-value burden and does so by enumerating returned data (both series, spreads, pagination, provenance, coverage). It still omits edge cases such as non-aligned dates or coverage-range limits and does not reference sibling alternatives.

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 fully documents all 7 parameters. The description only notes that Treasury aliases such as '10y' and '2y' are accepted, which duplicates the schema's own examples and adds no new parameter syntax or constraints.

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 operation: calculate a time series of one Federal Reserve Board H.15 rate minus another on aligned business dates. The term 'spread' and examples like '10-year minus 2-year Treasury spread' clearly distinguish it from sibling tools such as fed_board_h15_rate_history and fed_board_h15_yield_curve.

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?

Provides concrete use cases ('10-year minus 2-year Treasury spread', 'prime minus fed funds', 'compare 30-year and 5-year yields') and clarifies it is not a forecast or trading signal. However, it does not explicitly name alternative sibling tools or state when not to use it.

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