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

Annotations already declare readOnlyHint, idempotentHint and closed-world, so the safety profile is covered. The description adds genuinely new context beyond them: no authentication/API key is required, which is an operational fact an agent cannot get from the annotations. It does not mention result size or whether the catalog is static, which keeps it from a 5.

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 short sentences, front-loaded with what the caller gets, followed by the access note. No filler, no restatement of the name or title.

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?

With no output schema, the description usefully spells out the per-entry fields (JSON field path, unit, source), which is the key thing an agent needs in order to use the result for subsequent queries. What remains unstated is the approximate volume of the response and whether ordering is stable, a minor gap for a no-parameter tool.

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, so the baseline is 4 and there is nothing for the description to compensate for. The schema is fully closed (additionalProperties: false, empty properties), consistent with a no-argument catalog call.

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 enumerates exactly what the tool returns: every queryable subject (Treasury tenors/spreads, FX pairs, aggregates) along with its JSON field path, unit and source, which is effectively a schema catalog. That is specific enough to distinguish it from every sibling (history, briefs, samples, alert webhooks). It lacks an explicit verb, relying on the name/title for the 'list' action, so it falls just short of a 5.

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?

'Open, no API key needed' states an access prerequisite, and the content of the return (field paths) implies the natural workflow of calling this before get_history. But the description never says when to use this versus get_history/get_latest_brief or that it is a discovery step, leaving the sequencing to inference.

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