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

Annotations already indicate read-only, idempotent, non-destructive behavior. The description adds valuable behavioral details: it fuses three analyses (detect_changes, impact, test_impact), explains that test selection is a 'SAFE over-approximation' using reverse call-graph closure, and mentions handling of untracked files. This goes well beyond the annotations.

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 concise yet thorough. It front-loads the main purpose in the first sentence, uses a clear structure (colons, dashes) to break down the three fused analyses, and every sentence contributes meaningful information without redundancy.

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?

The tool has no output schema, but the description explicitly states the outputs: changed symbols, blast radius (dependents, risk tier, update sites), and test files. It also notes untracked files. While it doesn't detail return format, it provides sufficient completeness for an agent to understand what to expect.

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% with descriptions for all 5 parameters. The description does not elaborate on individual parameters beyond stating the overall purpose. While it provides context (e.g., test_depth for test selection), it adds limited value over 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?

The description clearly states the tool's purpose: it detects changes since a git ref, computes impact (blast radius, risk tier, must-update sites), and identifies test files to re-run. It explicitly contrasts with 'scout' as a post-edit companion, distinguishing it from a sibling tool.

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 advises using the tool 'right after editing, before running the suite' and positions it as 'the post-edit companion to scout.' This provides clear usage context and an alternative (scout), effectively guiding when and how to use the tool.

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