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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the safety profile is covered. The description adds a genuinely useful behavioral fact ('Spends nothing' — i.e., no quota/credit cost) and the diff ordering rule, but says nothing about whether the result persists as a named cluster, what identifier it gets, or whether repeated calls create duplicates.

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 definition is compact and front-loads the set-operation semantics with reinforcing examples; nothing is padded. It is somewhat run-on as a single colon-and-quote-laden sentence, which slightly slows parsing but doesn't waste words.

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 should say what the call returns (presumably a new cluster id), and it doesn't. Combined with the undocumented 'name' parameter, an agent can construct a call but cannot predict the result shape or confirm whether 'name' is required in practice.

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% — only 'clusters' carries a schema description, and the description's example plus the 'diff [from, minus]' note reinforces that parameter well and fully explains the 'operation' enum. However, the 'name' parameter gets no explanation at all in either schema or description, leaving a real gap.

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 makes clear this produces a new cluster from existing ones via set operations, and enumerates the three operations with a concrete example ('clusters [7, 3] keeps the domains of 7 that are not in 3'). It doesn't explicitly distinguish itself from the sibling create_cluster, but the set-operation framing is specific enough to infer the difference.

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?

Usage is implied through the operation semantics rather than stated: an agent can infer 'and' means intersection, etc., and the 'diff' entry states the arity constraint ('exactly two, order matters'). There is no explicit when-to-use vs. create_cluster guidance, and no statement about what happens to the source clusters.

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