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

Beyond the readOnlyHint=true / destructiveHint=false annotations, which correctly signal a non-mutating operation, the description discloses the LLM-backed implementation and, importantly, the graceful degradation to a heuristic when ANTHROPIC_API_KEY is missing — a real behavioral caveat an agent should know. With no output schema present, the stated return shape '{subject, body}' also adds genuine value.

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 short sentences, front-loaded with purpose followed by behavior and return shape, with no filler. The reference to src/lib/ai-commit-message.ts is an implementation detail that earns only partial keep as the context for the fallback behavior.

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 two-parameter generation tool this covers purpose, dependency, degraded-mode behavior, and return shape — enough to invoke it correctly without an output schema. The remaining gap is sibling disambiguation against the closely named commit-message and release-notes generators.

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 100%, with 'diff' documented as a unified-diff body and 'style' as 'conventional' (default) or 'plain'. The description adds nothing about either parameter, so the schema carries the full burden and the baseline of 3 applies.

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 opens with a specific verb and resource: 'Generate an AI commit-message-style description for a diff.' That is concrete enough to act on, but it never separates itself from the very similar sibling merjax_generate_commit_message, which the wording ('commit-message-style') arguably overlaps with.

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?

Usage is only implied: the required diff argument and the phrase 'for a diff' make it clear you call this when you have a diff and want PR text. There is no explicit statement of when to prefer this over merjax_generate_commit_message or merjax_generate_release_notes, and no exclusions or prerequisites are given.

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