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

Beyond the readOnly and openWorld annotations, the description discloses several important behaviors: it errors rather than returning a misleading 0% change, warns about later amendments, reports which filings were compared, can take tens of seconds, and costs $0.50 per call. This is rich, actionable behavioral context.

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 dense but efficient, front-loading the core purpose and then covering usage, failure modes, performance, and cost. A few extras like the evaluation link could be trimmed, but the structure is logical and every sentence carries useful information.

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?

Even without an output schema, the description explains enough about the result format, fallback behavior, failure conditions, latency, and authentication requirement for an agent to call the tool correctly. Nothing critical for invocation 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 adds value by explaining the role of accession parameters in controlling which filings are compared, and by clarifying that omitted accessions fall back to the two most recent filings. This goes beyond the schema's field-level descriptions.

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 names a specific verb ('diff') and resource ('a 10-K risk-factor or MD&A section'), and clearly states the output: added and removed passages plus a change ratio. This distinguishes it from sibling tools like filing_section or edgar_search, which fetch or search rather than compare.

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 gives concrete guidance on how to pin exact filings using accession numbers and what happens when they are omitted, including amendment warnings. It does not explicitly name alternative sibling tools or state when not to use this tool, but the intended context is clear.

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