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

The description makes the side effect clear (a write to the site timeline) and adds behavioral guardrails not in the annotations: one annotation per meaningful change, and commit/routes feeding compare_around's before/after reporting. Annotations already flag idempotent=false and destructive=false, so there is no contradiction.

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 with no filler; the first states purpose, the second gives the trigger and style rules, and the third explains optional parameters. All information is front-loaded and earns its place.

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 full schema coverage and an output schema present, the description covers the core decision points: when to call, how to phrase text, and when to enrich with commit/routes. It could add an explicit alternative/exclusion hint, but nothing necessary for correct invocation is missing.

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, but the description adds semantic value by explaining why commit and routes matter (they let compare_around scope before/after traffic) and by reinforcing text formatting. It does not substantially add to site or ts, but the overall contribution moves it above baseline.

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 uses a specific verb-resource pair ('Mark a moment on a site timeline') and concrete examples (deploy, content change, campaign start), plus an explicit trigger ('Call this every time you ship a change'). This clearly differentiates it from read/report siblings like list_annotations and compare_around.

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?

It provides a crisp when-to-use rule: every time a change is shipped, and it adds practical conventions (present-tense text, one annotation per meaningful change, include commit/routes when known). It does not explicitly list when-not-to-use or name alternatives, so it falls just short of full routing guidance.

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