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

Annotations already declare readOnly, idempotent, non-destructive, and non-open-world, so safety is covered. The description adds two useful facts beyond that — the source is the SEC IAPD public API and no API key is required — but says nothing about behavior on an unknown CRD, rate limits, or completeness/timeliness of the filing data.

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?

Front-loaded with the purpose sentence, then a tight bulleted when-to-use block, then a one-line source note — well organized and easy to scan. The enumeration of returned field groups is mildly redundant with the output schema that already exists, but it aids selection speed.

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 an output schema present, the description needn't explain return values, and annotations carry the safety profile; what remains — purpose, trigger conditions, prerequisite CRD source, data provenance and auth — is all present. Only failure modes on an invalid or missing CRD are unaddressed.

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 description identifies the operative parameter (CRD) and tells the agent where to get it, matching the schema's own note. However, the seven other parameters exposed in the nested schema (source_resource_id caching, wholesaler_ids scoping, exclude_fillers, additional_display_fields, etc.) are never mentioned, so the description adds little over the structured fields.

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+identifier: "Retrieve the full Form ADV filing detail for one RIA firm by its CRD number." It also enumerates the payload (client types, advisory activities, fees, custody, offices, affiliates), which distinguishes it from SearchIAPDFirm and from GetIAPDIndividualDetail without the agent opening either schema.

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 "Use this tool when" block gives three concrete triggers and names the prerequisite path (obtain CRD from SearchIAPDFirm), which is real routing guidance. It stops short of an explicit negative case such as "use GetIAPDIndividualDetail for a person CRD instead," so it is clear but not fully exclusionary.

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