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

Annotations already mark this as non-read-only and non-idempotent, so the description's main job is to add context. It adds that the operation creates a durable, owned record and requires the comparisons:write permission, which goes beyond what the annotations alone convey. There is no contradiction with 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 short and front-loaded, with the core action in the first clause and permission appended in a second sentence. The phrase 'usually one a comparison just created' is slightly awkward and hurts readability, but there is no redundant or filler content.

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 three-parameter creation tool with no output schema, the description conveys the main purpose, ownership constraint, and auth requirement. It does not clarify what a 'durable comparison' means, what the response contains, or how to source the three session IDs, leaving moderate gaps for an agent to resolve.

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 description coverage is 0%, so the description must compensate, but it does not explain set_id or map 'member run' to baseline_session_id clearly. 'Candidate run' aligns with candidate_session_id, but the description leaves the relationship between the terminology and the schema largely implicit.

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 identifies a specific action ('Record one durable comparison') and resource (a comparison artifact), and the ownership qualifier adds useful scope. It does not explicitly differentiate itself from siblings like run_comparison or create_comparison_verdict, but the persistence-oriented wording makes the intent reasonably clear.

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 phrase 'usually one a comparison just created' gives a temporal hint about when to use the tool, and 'you own' implies an eligibility condition. However, it is ambiguous and does not state when not to use it or name more appropriate sibling tools such as create_comparison_verdict or run_comparison.

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