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

With no annotations, the description carries the full burden. It discloses important behavioral traits: as-reported data, point-in-time semantics via as_of, restatement handling via history, and the data source. It also lists returned fields (period, value, fiscal year/period, SEC form, accession, filed date). Lacks details on auth, rate limits, or error behavior, but the core behavior is transparent.

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 three sentences, front-loaded with the core definition, followed by usage guidance and a pointer to the tag search endpoint. Every sentence adds value with no fluff.

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 10 parameters and no output schema, the description gives a solid overview and key parameter semantics, but omits details on six parameters and does not describe return structure or edge cases. It is adequate for an experienced user but not fully complete.

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 only 20%, so the description must compensate. It adds meaningful semantics for as_of and history, explaining their effect on restatement look-ahead. However, it leaves start, end, form, unit, limit, and taxonomy unexplained. Partial compensation for the low schema coverage, but significant gaps remain.

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 clearly states the tool's function: providing one XBRL concept's as-reported history from the SEC EDGAR companyfacts corpus. It uses a specific verb ('history') and resource, and distinguishes itself from sibling tools by emphasizing exact as-filed fundamentals and referencing /fundamentals/companyfacts for tag discovery.

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 gives explicit guidance on when to use the tool ('Call it for exact as-filed fundamentals') and explains the key parameters as_of= for point-in-time (no restatement look-ahead) and history=true for all restatements. However, it does not explicitly name alternative tools or state when not to use it.

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