Insider buys by ticker, today, or a date range (SEC Form 4)

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantive context beyond them: the signal-filter caveat ('only purchases that pass the signal filter are returned; code P is not proof of a buy'), the meaning of offering_context, and the fact that source_excerpt is quoted filing data, never derived.

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 dense paragraph, front-loaded with the usage trigger followed by parameterization, return-field notes, and the caveat. Every sentence carries information, though the packing is heavy enough that it borders on overload.

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?

Despite having no output schema, the description explains the returned row fields (filing_url, offering_context, source_excerpt), the default-time behavior, and the filtering caveat, and the schema itself covers pagination. Nothing an agent needs to call it correctly 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 baseline is 3; the description earns above it by adding behavioral meaning to the parameters, notably that supplying neither ticker nor start/end defaults to today's buys, that `days` narrows, and that `include_unlisted` admits non-listed issuers.

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+resource ('which insiders bought a stock', 'Form 4 buys') with clear scope. It does not, however, explicitly differentiate itself from the closely related sibling insider_cluster_buys, leaving some ambiguity for an agent choosing between the two.

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?

Opens with an explicit 'Use when...' trigger covering the three request shapes (specific ticker, ticker-level buying check, date range) and then explains how to parameterize each case. It stops short of stating when NOT to use it or naming a sibling alternative, so it is strong but not fully routing.

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