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

With no annotations available, the description carries the full burden of behavioral disclosure. It reveals the filtering rule, temporal scope, ranking order, and a constituent field. It does not mention empty-result behavior or read-only status, but for a simple no-parameter query tool this is reasonably transparent.

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 a single dense sentence that front-loads the core purpose ('Rule-2 insider-buy signals filed today') and then adds essential qualifiers. There is no redundancy or filler; every clause adds meaningful detail.

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?

For a zero-parameter tool with no output schema, the description covers the key selection criteria and a result characteristic (filing_url). It could list additional return fields, but the provided detail is sufficient for selecting and invoking the tool correctly.

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 has zero parameters, so the input schema is empty and schema description coverage is trivially 100%. The description appropriately contains no parameter information, matching the baseline of 4 for tools without parameters.

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 states the exact resource (Rule-2 insider-buy signals), the temporal scope (filed today), the SEC code (P open-market purchases), the ranking (cluster-first), and a key field (filing_url). This clearly distinguishes it from siblings like insider_signals_by_date_range and insider_signals_by_ticker without needing to open schemas.

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 description implies the tool is for today's signals ('filed today'), but it does not explicitly say when to use it versus alternatives or mention sibling tools. No exclusions are provided, so guidance relies on inference rather than direct routing.

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