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

The description goes well beyond the readOnly/idempotent annotations: it discloses that the service never recomputes comparisons, refuses unsupported pairs by returning the published URL, and treats reversed requests as the same artefact with inverted operations. This gives the agent critical behavioral expectations not available from annotations alone.

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 and contains no filler; every clause conveys a constraint or behavior. It is somewhat run-on with heavy em-dash usage, which slightly reduces scanability, but it is still compact and information-rich.

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?

Given the output schema and annotations, the description provides everything an agent needs to decide whether to call this tool and what to expect: supported pairs, refusal behavior, no recomputation, direction symmetry, and the fact that it is a read-only idempotent operation. The unusual 'servable iff diff artefact exists' restriction is fully explained.

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 covers most parameter meanings, and the description adds useful semantic context: the two version ids must belong to the same instrument, and their order is reversible with the operation direction inverted. It does not describe pagination parameters, but those are adequately implied by limit/cursor and the existing output schema.

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 states a specific operation: returning a word-level comparison of an article between two versions of the same instrument. It also clearly delimits the scope to precomputed diff artefacts (PSR and PSD3 proposal↔compromise pairs), which distinguishes it from generic comparison or retrieval tools like list_version_changes or get_provision.

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 explicitly says a pair is servable if and only if a diff artefact exists, names the only supported pairs, and states that every other pair is refused. It gives a clear when-to-use rule and an explicit exclusion, though it does not name alternative sibling tools for the refused cases beyond pointing to the published URL.

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