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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorld, so the safety profile needs no restating. The description adds real substance beyond that: the breadth of the payload (co-issuers, related persons with CRD numbers, sales compensation recipients, filer notes, signatures) and the ordinal ordering of offering_history, which tells the agent the response is a complete single-filing record rather than a summary.

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-loaded with the action and the key argument, followed by a payload inventory and an args block. The middle sentence is a long comma-and-semicolon enumeration, but each listed field group carries distinct information; only the offering_history gloss is close to excess given an output schema exists.

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 a single-parameter lookup with an output schema and full safety annotations, the definition covers the entry path, the identifier format, and the scope of the returned record. The remaining gap is failure/not-found behavior, which is minor here.

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 carry the parameter, and it does: it names the argument "accession_number" as a Form D accession number and supplies a concrete format example ("0001104659-26-114962"). It still does not say whether the dashed or undashed form is accepted, which keeps it below a 5.

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 opening line gives a specific verb and resource ("Get one Form D filing in full, by accession number") and immediately attributes the identifier to its sibling search_private_offerings. An agent can distinguish this from search_private_offerings without opening either schema.

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?

Naming "(from search_private_offerings)" makes the intended workflow explicit: search first, then fetch the full record by accession number. There is no statement of when-not to use it or of failure behavior for an unknown accession number, so it stops short of full when/when-not guidance.

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