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

With annotations already declaring readOnlyHint=true and destructiveHint=false, the description adds valuable behavioral context: the fallback logic when artifact_document_id is omitted (resolves latest filing) and the registry-specific TOC node id formats (HTML vs sec-parser ids). These details go beyond the schema and annotations, disclosing expected output structure.

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 long, front-loaded with the primary purpose, then conditional behavior, then registry-specific notes. No filler or repetition exists; every sentence earns its place.

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?

Despite lacking an output schema, the description communicates what the TOC contains (node ids) and how to interpret them per registry. It covers the essential edge cases (omitted artifact_document_id, FCA specifics) without overwhelming detail. A slight gap is not mentioning the overall return shape, but this is acceptable given the complexity and sibling context.

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 40%, leaving ticker, company, and artifact_document_id undocumented. The description compensates by explaining artifact_document_id's role in resolving the latest filing, and it clarifies filing_registry usage for FCA. While ticker/company are self-explanatory, the description effectively fills the gaps for the trickier parameters.

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 opens with a specific verb+resource ('Return the full filing table of contents for one filing'), making the tool's core function immediately clear. It also distinguishes itself from siblings by explicitly referencing list_filings for discovery, and the mention of FCA node id formats highlights its unique role in returning TOC structure rather than content.

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?

The description provides a direct usage guideline: 'Use list_filings first to discover a specific reporting period.' It also gives conditional guidance for FCA filings with 'pass filing_registry=fca_nsm'. However, it does not explicitly mention when to use get_latest_filing or read_node_content as alternatives, so it lacks full exclusionary guidance.

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