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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds useful behavioral context beyond those annotations: it states the data source (SEC EDGAR API), that no API key is required, and that the tool returns every filing on record. It does not cover rate limits or pagination, but the annotation coverage lowers the bar.

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 well-structured and front-loaded with the core action, followed by concrete use cases, a CIK lookup link, and source/authentication notes. There is slight overlap between 'tracking all regulatory disclosures' and the later 13F/ADV bullet, but no significant waste.

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 read-only API-backed tool, the description provides enough context to select and invoke it: it names the required domain identifier, shows where to find it, explains the returned data, and notes that no API key is needed. An output schema exists, so return-value documentation is not the description's burden. Minor gaps include no explicit mention of rate limits or pagination.

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 nested schema already documents the parameters in detail, including CIK formatting and zero-padding. The tool description adds some context around CIK usage and the return of accession numbers, but it does not meaningfully expand on the parameter semantics beyond what the schema provides. Baseline 3 is appropriate because the schema carries the parameter documentation burden.

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 a specific verb and resource: 'Retrieve all SEC filings for a company or institution using its CIK.' It also clarifies the returned content (form type, date, accession number, description) and the all-filings scope, which distinguishes it from more targeted siblings like SearchEdgar13F or Get13FHoldings.

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 explicitly lists 'Use this tool when' scenarios: having a CIK, tracking 13F/ADV/ownership disclosure history, and needing accession numbers. This provides clear when-to-use guidance, though it does not explicitly name alternative tools or state when not to use it, so it falls just short of a 5.

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