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

Annotations already declare readOnly/idempotent/open-world, so the bar is lower. The description adds real substance beyond them: results are XBRL facts tied to the accession, scoped to ten supported concepts, capped at 200 values with units and periods. It does not cover auth requirements or failure modes, but the coverage is solid.

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, use-case front-loaded, and the null-result boundaries are tacked on efficiently. The 'does not give investment advice' clause is filler that does not help tool selection, keeping it short of a 5.

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 annotations covering safety semantics and an output schema covering return structure, the description supplies the remaining essentials: what is returned (XBRL facts), the concept ceiling, and the value cap. The one real gap is filing_id format guidance, which neither the schema (0% coverage) nor the description addresses.

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 0%, so the description must compensate. It hints at the cap ('up to 200 reported values') and that facts are tied to the accession, but never explains the filing_id format/pattern or the limit default of 50 and its 1-200 range. Partial compensation only.

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 concrete verb+resource (return XBRL facts tagged to a filing accession) and states scope ('in one filing'). It differentiates implicitly from compare_filing and list_filings, but never names a sibling tool, so an agent still has to infer which one to pick for section text versus numbers.

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?

'Use when someone asks for the reported numbers in one filing, such as revenue, net income or total assets' gives a clear triggering context with concrete examples. It also states two exclusions (not all periods for a company; not investment advice), though the second is a compliance boundary rather than a genuine routing alternative.

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