Diff between versions

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds the return format (unified diff) and that output is scoped to a single file, which is useful given there is no output schema, but it says nothing about size limits on large diffs, pagination, or how missing versions are handled.

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?

A single front-loaded sentence with no filler; the most important scoping information (one file, unified format, between two versions) comes first and the version-number source is parenthetically appended.

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 4-parameter tool with no output schema and low schema coverage, the description covers the critical question of where version numbers come from but omits path conventions, error behavior for versions that don't exist, and any indication of diff output size. Adequate but with clear gaps.

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 25% (only `project` is documented), so the description must compensate. It clarifies the meaning and source of `fromVersion`/`toVersion` beyond the bare integer schema, but leaves `path` (format, project-relative vs absolute) and the omitted-project pinning behavior to the schema alone.

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?

States a specific operation (unified diff) on a specific resource (one file between two history versions), which is unambiguous. It implicitly separates itself from the sibling `history` tool by noting that the version numbers come from that tool, but it does not explicitly frame the sibling relationship beyond that hint.

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 parenthetical gives real usage context: the fromVersion/toVersion values must be obtained from the `history` tool's vFrom→vTo numbers, establishing a prerequisite workflow. It stops short of stating when-not to use it or naming an explicit alternative for viewing differences.

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