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

Annotations already declare readOnlyHint/destructiveHint, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: a 204800-byte cap, the startLine/endLine escape hatch for large files, and the caveat that renames are not tracked.

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 with the core operation front-loaded and no filler. Dense but every clause carries information; only minor compression could improve it.

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 carries the burden of describing return content, and it does so (ranges attributed to a sha; commits with title, message with task keys, author, dates). The size limit and rename caveat round out what an agent needs 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%, so the baseline is 3. The description goes slightly beyond by explaining that startLine/endLine exist to page through large files and implying ref selection semantics via the fix-commit-parent example, adding intent the schema text does not.

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 and resource: 'Returns line-by-line blame of a file at a ref', and enumerates the two output groupings (ranges and commits). This is clearly distinct from repo_history/repo_search in intent, though the near-sibling repo_line_history is never named or contrasted.

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 an implied usage scenario ('Blame at the parent of a fix commit shows the lines as they were before the fix'), which helps the agent reason about ref selection. It does not state when to prefer this over repo_line_history or repo_history, so the routing guidance is only implied.

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