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

Annotations cover the read-only/idempotent safety profile, and the description adds substantial context beyond them: the $1.00 USD commercial model, the abstention-before-payment behavior ('Returns a number only when deterministic context compatibility is established; otherwise abstains before payment'), and the validation/provenance guarantees. This is exactly the kind of pricing, failure-mode, and auth context annotations cannot express.

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 sentences, each carrying distinct information (capability, abstention semantics, routing guidance), and the preflight instruction is placed last where an uncertain agent needs it. The opening '$1.00 USD specialist operation when commerce is active' is slightly cryptic and front-loads pricing over purpose, costing a point.

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, return-value structure needn't be explained, and the description covers the commercial trigger, the abstention condition, and the eligibility escape hatch. It is nearly complete, though the vague 'when commerce is active' qualifier and lack of detail on what a failed/abstained call returns leave a small gap.

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%, so all five parameters (cik, metric, period_start/end, anchor_accession) are already documented in the schema, including the enum values the description repeats. The description adds no format, default, or boundary details beyond what the schema provides, so the baseline 3 applies.

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+resource ('Return the correct standalone-quarter revenue, net income, or operating cash flow as reported through SEC filings') and enumerates the exact metrics, so an agent can distinguish it from sibling tools like build_evidence_pack or compare_filings. The anchoring mechanism (cumulative-period subtraction) further narrows its scope.

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?

It explicitly names when to route elsewhere: 'Use filedproof.preflight_financial_fact or POST /v1/research/financial-fact/preflight first when eligibility is uncertain.' That is a concrete precondition naming an alternative. It stops short of stating when NOT to use the tool (e.g., non-quarterly periods or unsupported issuers), so it is clear but incomplete.

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