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

Annotations already declare readOnlyHint=true and destructiveHint=false; 'without writing' largely restates this. It does confirm the dry-run semantics against a mutating sibling, which adds modest value, but it doesn't explain what the report contains or how conflicts in `prefer` are surfaced.

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?

A single sentence with the key distinction (report vs. apply, no writes) front-loaded. Nothing wasted.

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 dry-run/validation tool with no output schema, the agent gets no sense of what the report looks like (diff format, conflict warnings, error reporting). Adequate for a safe read, but thin for a preview tool whose whole value is its output.

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%, so all five parameters (including rev, prefer, edits, source) are already documented in the schema. The description only echoes 'edits or source' and adds no format or conflict-resolution detail beyond the structured fields.

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 (report) and a precise relationship: it reports what apply_timeline would change for the same edits or source. This distinguishes it cleanly from apply_timeline without needing the schema.

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 phrase 'without writing' implies the preview-before-apply use case, and naming apply_timeline points at the alternative. But it never explicitly says when to call this versus applying directly, nor does it mention any prerequisites or exclusions.

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