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), yet the description adds substantive context: it reads stored SEC XBRL data only, segment definitions differ between issuers, comparison mode returns not_found and coverage_notes, and filing evidence references resolve into sources[]. These are the failure and trust characteristics an agent needs before calling.

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-loads the capability, then organizes by mode with parameter glosses followed by return shapes — a logical progression with no filler. The telegraphic, fragment-heavy style ('year pins the fiscal year') is efficient but occasionally reads as shorthand notes rather than prose.

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 an 8-parameter tool with an output schema present, the description covers modes, parameters, return structure, and data provenance. The single omission is the quarterly/annual toggle, which an agent must infer from the schema alone.

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?

With 0% schema description coverage across 8 parameters, the description carries the full burden and mostly succeeds: it enumerates metric values, axis values, the periods default of 8, year semantics, and the cross-axis behavior of member_filter. The notable gap is period_type (quarterly/annual), which is never mentioned despite being the only enum-constrained parameter.

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 and resource ('Retrieve US company segment metrics across fiscal periods') and defines the dual scope: one company or 2-5 side by side. The segment-level framing implicitly separates it from the consolidated get_company_financials sibling, though no sibling is named explicitly.

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?

Clearly explains the two operating modes — single-company lookup versus 2-5 company comparison — and maps parameters to each mode. It does not state when-not to use it or point to alternatives like get_company_financials for consolidated totals or get_revenue_geography for geographic-only views.

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