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

Annotations already establish readOnly, idempotent, non-destructive and closed-world behavior, so the safety profile needs no restating. The description adds genuinely useful behavioral context beyond them: the report is deterministic, and the INSUFFICIENT_INPUT result code signals a failure mode. It stops short of describing malformed-XML error behavior, so not a 5.

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 core purpose and the two-parameter contract come first, followed by return shape, then the large-document escape hatch. The return-value enumeration is dense but warranted because no output schema exists; no sentence is filler.

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 read-only two-parameter comparison with no output schema, the description supplies everything needed: input meaning, result code vocabulary, the issue record fields, example change codes, and an explicit alternative for oversized inputs. Nothing needed to invoke it correctly 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 0%, so the description carries the burden, and it does define both parameters semantically: old_nodeset_xml is the full baseline revision and new_nodeset_xml the full candidate revision. It also implies each must be an entire document rather than a fragment. It doesn't note encoding/size constraints, keeping it at 4.

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 verb (compare) and resource (two complete OPC UA NodeSet2 XML documents) and scopes it to the single-request case. It clearly separates this tool from the sibling audit_uploaded_nodesets, which handles the chunked-upload path, so an agent can pick correctly without opening schemas.

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?

Explicit guidance on when to use this tool ('when both fit in a single request') and a named alternative workflow for when not to ('For large XML documents use begin_nodeset_upload + append_nodeset_chunk ... then audit_uploaded_nodesets'). That is a complete routing decision, including the sibling names.

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