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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds value with the 'Free' cost note and the stable-id matching semantics, but says nothing about output shape, pagination, or behavior on invalid refs beyond what annotations supply.

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 dense sentence that front-loads the free-cost signal and the result categories. Efficient, though the subject of the sentence is elided, making the opening slightly clipped.

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 free, read-only diff with three simple string parameters and no output schema, the definition covers cost and matching semantics but leaves the return structure and the from/to asymmetry (to defaults to main, from is required) unexplained, which an agent would need before calling.

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 only 33%: model_id is documented in the schema, but from and to have no descriptions. The description partially compensates by establishing that from/to are commits, branches or baselines, yet it never states that 'to' defaults to main or clarifies the semantics of the required 'from'.

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 (diff) and resource (elements between two versions), naming the four result categories (added, removed, changed, renamed) and the matching key (stable id). It is distinguishable from siblings like mbe_drift or mbe_commit, though it does not explicitly name an alternative.

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?

Implies usage by mentioning commits, branches and baselines as endpoints, and the 'Free' note hints at cost considerations relevant elsewhere in this suite (estimate_cost, get_credit_balance). However, there is no explicit when-to-use-this-vs-mbe_drift guidance and no stated prerequisites.

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