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

The description says it produces a 'readout' (a non-mutating report), but the annotations include destructiveHint=true. This is a contradiction: a readout implies no destruction, and the description does not mention any destructive side effects. No additional behavioral context is added beyond the annotations.

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 two sentences that are packed with specifics, no filler, and the core concept (structural difference) is front-loaded. The second sentence adds context about when it's useful.

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 no output schema, the description gives the categories of changes detected but does not describe the shape or format of the returned readout, nor does it address the destructive behavior indicated by annotations. For a diff tool, this leaves an agent uncertain about what response to expect and what side effects may occur.

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?

The schema provides full descriptions for both parameters (a: model id before; b: model id after), and the description adds the notion that these are ids in a lineage, which is a small semantic enhancement. But overall the schema already carries the meaning, so baseline 3 is appropriate.

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 clearly states it computes a structural difference between two stored models, listing specific categories of changes (places, transitions, arcs, numeric attribute changes). It connects to the lineage context of builder turns, sim_extend, and sim_refine, which helps distinguish from those tools. However, it doesn't explicitly differentiate from sim_compare, so there is some ambiguity among siblings.

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 description implies when to use it: when you need the readout of what a builder turn, sim_extend, or sim_refine changed between two ids in a lineage. But it doesn't provide explicit guidance on when not to use it or mention alternatives like sim_compare. The context is helpful but not prescriptive.

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