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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description goes beyond them by disclosing that each value carries an as-of date, that week- and month-earlier readings appear only 'when available', and that a freshness status and publisher link are included — real signals about possibly stale data and variable presence of fields. It stops short of stating units (e.g. percent) or whether multiple entries per tenor are returned.

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?

It is a single front-loaded sentence that leads with the instrument tenors and then the metadata fields, with no filler. It is dense — the 'each with its...' clause runs long — but every element listed corresponds to a returned field, so nothing is wasted.

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?

There is no output schema, so the description carries the burden of describing the shape of the result, and it does so by enumerating series, as-of dates, prior readings, freshness and source links. Given zero parameters and full annotation coverage, this is nearly sufficient; only units/format of the yields and the precise structure of the response remain unstated.

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?

The tool takes zero parameters, which is the baseline-4 case; there is nothing for the description to disambiguate. The description correctly implies a no-argument 'fetch latest snapshot' call by never referencing any filter or option.

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 names a specific resource (5-, 7- and 10-year Treasury par yields plus overnight SOFR) and enumerates the accompanying fields, so an agent knows exactly what this returns. It also implicitly separates itself from the program-focused siblings by being macro-rate data, though it never names compare_programs or get_program_terms to state the boundary explicitly.

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?

Usage is only implied: the phrase 'that the multifamily.online app builds its example rate on' hints this is the benchmark-rate lookup to use when explaining pricing context. There is no explicit when-to-use statement, no exclusions, and no mention of the sibling tools, so the agent must infer the routing decision.

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