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

Annotations already mark readOnlyHint=true, and the description adds non-obvious behavior: the exactly-one identifier rule, the default diff target, and the full return shape. It does not discuss failure/error behavior, but the read-only annotation lowers the burden.

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 dense but well-structured: purpose first, then identifier selection rules, default behavior, and return shape. Every clause carries useful information without padding.

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?

Since there is no output schema, the description compensates with an explicit return shape covering from/to endpoints and the diff summary. Combined with the rich input schema and read-only annotation, an agent has everything needed to invoke it correctly.

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 schema already documents each property. The description still adds value by applying the exactly-one rule across both `from` and `to` (the schema only states it on `from`), and by surfacing the stable-sha256 preference in one place.

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: 'Compute a semantic diff between two model revisions' and enumerates the diff categories (added/removed/modified items plus metadata changes). This clearly distinguishes it from version-listing/restoration siblings even without naming them.

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 gives concrete guidance on identifier selection ('exactly one of', revision_id preferred) and the default behavior when `to` is omitted. It does not explicitly compare against sibling tools such as layerz_history or layerz_restore_version, so it stops short of full alternative routing.

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