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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description usefully adds behavior beyond that: patch text is byte-capped and output can be truncated, and it shows the return shape. However it does not explain what truncation means for the caller (e.g., how to retrieve the remainder) or hint at size/permission limits.

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?

Three tight sentences, front-loaded with the operation, then the two calling modes, then the return shape and the size control. There is no filler, and each sentence carries decision-relevant information.

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?

With no output schema, the description steps in by sketching the returned object ({files, stats, truncated}) and the fields per file. For a 7-parameter read tool with two mutually exclusive calling modes, that is close to complete; only the exact truncation/retrieval semantics and max_patch_bytes guidance are missing.

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 71%, and the description adds real meaning beyond it: it specifies that `sha` diffs against the first parent and that base/head uses the merge base, plus the practical effect of include_patch=false. The `max_patch_bytes` parameter is only indirectly covered by 'byte-capped', leaving its tuning semantics to the schema.

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 verb ('Read') and resource ('actual changes in a commit or a branch range'), and 'actual changes' implicitly distinguishes it from metadata readers like merjax_get_commit or merjax_get_pr. It stops short of naming any sibling explicitly, so the differentiation is inferential rather than stated.

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?

Gives explicit mode-selection guidance: pass `sha` for a single commit vs its first parent, or `base`+`head` for everything head adds since the merge base, framed as 'what a PR proposes'. It also offers a lightweight alternative ('set include_patch=false for a files-changed summary only'). No sibling-tool routing is offered, which keeps it from a 5.

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