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

Annotations already declare the tool read-only, idempotent, and non-destructive. The description adds meaningful context beyond that: it explains the 5% ownership threshold, the 13D vs 13G distinction, and that the output links to the filing. This is useful behavioral context without contradicting the annotations.

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?

The description is compact: three sentences that front-load the resource, then state the key outputs and the activist/passive interpretation. Every sentence earns its place with no repetition or filler.

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 a rich output schema, comprehensive annotations, and only three parameters, the description covers the essential semantics of the tool: what filings it searches, what facts it returns, and how the 13D/13G distinction should be interpreted. No critical operational context is missing.

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%, so the schema already documents ticker, days, and limit. The description adds domain context like 'US-listed' and the 5% threshold, but it does not add parameter-level meaning beyond what the schema provides, so the baseline 3 is appropriate.

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 identifies a specific resource (SEC Schedule 13D and 13G beneficial-ownership filings), a clear subject (US-listed company), and the concrete outputs (who crossed 5%, date, filing link). It also adds interpretive value by distinguishing 13D activist intent from 13G passive intent, which separates it from sibling tools like insider_trades or insider_8k.

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?

The final sentence, 'Answers who has accumulated a large stake in a company,' gives a clear context for when to use the tool. It does not explicitly name alternatives or exclusions, so it stops short of full guidance, but an agent can infer the appropriate use case.

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