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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description earns credit for adding beyond them: it discloses the signal-filter semantics ('only purchases that pass the signal filter are returned') and the error behavior when no gated filing matches.

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?

Three tight sentences, front-loaded with what is returned and followed by the filter caveat and error case. No filler, though the trailing 'with their filing_url' clause is slightly tacked-on.

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 no output schema, the description sensibly conveys the return content (signal records plus filing_url) and the error path. For a single-parameter, fully-annotated read tool this is nearly complete; only pagination/record-count behavior is unaddressed, and it may be unnecessary.

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 description coverage is 100% and the single accession parameter already carries a format example, so the description adds no syntax or format detail. Baseline 3 is appropriate when the schema does the heavy lifting.

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: retrieves Rule-2 signal records for one SEC filing accession. This clearly separates it from siblings like insider_signals_by_ticker or verify_insider_purchase, though the 'Rule-2 signal' jargon is domain-specific and not explained.

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?

Usage is implied by 'lookup by accession' and the mention of filing-level records, but the description never explicitly says when to pick this over insider_signals_by_ticker or the verify_* siblings, nor what prerequisite (having an accession) drives its selection.

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