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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the key behavioral fact that revisions are 'immutable', implying the comparison is safe and non-mutating, and clarifies that omitting 'to_revision' defaults to the latest version. This adds useful context beyond the annotations without contradicting them.

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 extremely concise: two sentences with no filler. The core purpose is stated first, followed by a single actionable tip. Every word earns its place, and it's front-loaded with the verb 'Compare'.

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 tool with 3 parameters (one optional) and an output schema, the description covers the essential use case and the optional parameter behavior. It references 'immutable revisions', giving context about the data model, and the output schema handles return values. The only minor gap is the lack of explicit definitions for 'symbol' and 'from_revision', but these are reasonably inferable from the tool name and domain context. Overall, it's sufficiently complete for an agent to call correctly.

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 only explains the 'to_revision' parameter ('Omit to_revision for latest'), but provides no explanation for 'symbol' or 'from_revision'. While these are somewhat intuitive from the tool name, the description does not explicitly define their meaning or format, leaving a significant gap given the lack of schema descriptions.

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 action ('Compare') and the resource ('company revisions'), and specifies the content compared: 'facts, assumptions, scenarios and thesis'. It also distinguishes itself from the sibling 'compare_company_history' by focusing on revisions, though it doesn't name that sibling. The purpose is unambiguous and specific.

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 one explicit usage guideline: 'Omit to_revision for latest', which tells the agent when to omit an optional parameter. However, it does not provide guidance on when to choose this tool over alternatives like 'compare_company_history' or 'get_company_revisions'. There is no explicit when-to-use or when-not-to-use context beyond the parameter tip, so it's adequate but incomplete.

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