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

Annotations only declare readOnlyHint, and the description meaningfully extends that: it discloses the output shape (ranges attributed to a commit sha plus commit metadata), a 204800-byte cap with the startLine/endLine workaround, and the 'renames are not tracked' limitation. Missing pagination/error behavior, but the added operational constraints are substantive.

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 dense sentences with the core purpose front-loaded and no filler. The output-format clause is packed tightly, which slightly strains readability but every clause carries 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 carries the burden of explaining returns and does so (ranges, commits with title/message/author/dates), plus byte limits and rename behavior. Auth/prerequisite context is absent but not critical for a read-only query.

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 each parameter is already documented at baseline 3. The description adds value by explaining the purpose of startLine/endLine (range reads for large files) beyond the schema's mechanical definition, slightly clarifying their role.

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 even outlines the return structure (ranges and commits). It is easy to distinguish from generic list/search tools, though it never names the closest sibling (repo_line_history) to draw a hard boundary.

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?

Offers one concrete usage scenario ('blame at the parent of a fix commit shows the lines as they were before the fix'), which implies when the tool is useful, but gives no explicit when-to-use/when-not guidance or routing against sibling tools like repo_line_history or repo_history.

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