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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real value beyond that: it discloses that the record is the 'full register entry' with dated deadlines and a source URL plus last-verified date, which signals data freshness semantics the annotations do not convey.

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?

A single sentence, front-loaded with the verb and resource, then the payload contents. No filler, no restatement of the tool name or annotations.

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 must carry the return-value burden, and it does so by enumerating the fields an agent will receive. Combined with annotations covering safety, an agent has everything needed to call it correctly and anticipate the response shape.

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?

With 100% schema coverage on a single parameter, the baseline is 3, and the schema example ids already document format. The description still adds provenance meaning by stating the id comes from search_instruments, clarifying that this is not an arbitrary identifier but a register key produced by the sibling tool.

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 (get) and resource (one instrument from the register) and enumerates the returned content: formal name, reference, issue date, status, bindings, deadlines, regulator URL, last-read date. It also distinguishes itself from search_instruments by noting the id's provenance, so an agent can tell it apart from the sibling search tool.

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 explicitly says the id comes 'from search_instruments', which routes the agent to the correct upstream tool and implies this is a follow-up detail lookup rather than a discovery call. It stops short of stating when NOT to use it (e.g., for bulk retrieval use search_instruments), so it is clear context without explicit exclusions.

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