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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), and the description adds genuine behavioral context on top: exact-match semantics, candidate fallback on non-exact input, the full shape of the response (status, years on the Clock, open-since date, as-of date, page and filing links), and a guardrail against inventing a status. That is information the annotations cannot supply.

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?

Purpose is front-loaded in the first clause, followed by return shape, matching rules, and the guardrail in descending priority. Roughly four sentences with no filler, though the candidate sentence is slightly run-on and could be split.

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 one parameter, no output schema and simple annotations, this description covers everything an agent needs: what it accepts, how matching works, what comes back, and what to do when the match is not exact. There is no output schema to defer to, and the description compensates by listing the returned fields.

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% on a single parameter, so the baseline is 3. The description earns above baseline by clarifying that matching is exact on ticker, CIK or full name, which tells the agent partial names will not resolve and will instead trigger the candidate path.

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 (looks up) and a precisely scoped resource (one public company) and enumerates the three accepted identifier forms. The scope word "one" implicitly separates it from the sibling headline tool, so an agent can tell what this returns without opening the schema.

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?

Gives a clear operating context plus a decision rule for the ambiguous case: fuzzy input returns candidates and the agent should ask the user which company is meant. It does not explicitly name clock_headline or state when not to use this tool, so it stops short of full alternative routing.

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