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

With no annotations, the description carries the full burden and does substantial work: it discloses the per-factor status enum, the presence of sentence-level key_changes, that `severity` is a legacy deterministic 1-10 score, that `ai_bump` is always 0 and `ai_brief` is always null, and that related passages are evidence rather than proof of exposure. What it leaves out is operational behavior such as error handling for an unknown ticker or one year missing a filing, which is why it falls short of a 5.

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?

Purpose is front-loaded in the first sentence and the remaining sentences each add distinct information about the payload: status enum, key_changes, severity semantics, the two guaranteed-null fields, and the interpretive caveat. The deprecated-field notes are the least valuable content but are short enough to earn their place as guards against misreading the response.

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?

There is no output schema, so the description must explain the return shape, and it does so reasonably well: factor statuses, key_changes, severity components, disclosure_overview, and the interpretive limits of the scores. It is weaker on failure modes and on whether UNCHANGED factors are included in the 'full' diff, which an agent would want before calling.

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 coverage is 100% and all three parameters are required with example formats already in the schema, so the baseline of 3 applies. The description adds only the relational meaning that the two years form a comparison window; it never states the ordering constraint that year_current must be later than year_prior or what happens if they are inverted.

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: 'Get the full 10-K risk factor diff for a company between two years,' naming the document type (10-K), the section (risk factors), and the comparison axis. It does not distinguish this tool from the closely related sibling list_company_diffs, so an agent must infer that this one returns detail for a single company pair while the sibling enumerates.

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?

There is no explicit guidance on when to call this versus list_company_diffs, get_signal, or list_companies, and no stated preconditions such as both years needing filed 10-Ks. The only usage-adjacent content is interpretive guidance about how to read the returned sections, which tells the agent how to consume results rather than when to invoke the tool.

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