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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering the safety profile. The description adds genuine edge-case behavior beyond that: unknown CIKs or companies lacking XBRL data return an empty series, and results come newest fiscal year first.

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 tight sentences with no waste. The core purpose and ordering lead, the empty-result caveat follows, and sibling routing closes the definition.

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?

An output schema exists so return values need no elaboration, and annotations carry the read-only/open-world profile. The description covers the key empty-series edge case and sibling routing, leaving only minor param details (limit, period) to the schema.

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 the schema already documents cik, statement, period, from, to, and limit including allowed values. The description reinforces statement types and the newest-first ordering but adds no syntax or format detail beyond the schema, matching the baseline 3.

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 (Fetch) and resource (SEC-reporting company's normalized income-statement, balance-sheet, or cash-flow history) keyed by cik. It explicitly distinguishes itself from siblings datasets_sec_companies_item and datasets_sec_companies_insider, so an agent can route without opening schemas.

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 names two sibling alternatives with their distinct purposes ('company details', 'insider filings'), making the selection condition implicit but clear. It also states the result ordering (newest fiscal year first). No explicit when-not-to-use beyond the sibling routing.

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