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

Annotations already flag destructiveHint=true and idempotentHint=true; the description explains why destruction occurs ('entries replaces the whole ordered list') rather than restating the hint. It also discloses a gating requirement the annotations cannot carry: 'Collections are part of Volley Pro.' It does not say whether updating a collection also overwrites the untouched title/visibility fields.

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?

Three compact sentences, front-loaded with the create/update decision, then entry semantics, then the entitlement note. Every clause carries information an agent needs and nothing is padded.

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 mutation tool with annotations present and no output schema, the description covers upsert behavior, destructive replacement semantics, entry shape, and the Pro entitlement. The remaining gap is partial-update behavior for non-entries fields, which the agent cannot infer from either the description or the schema.

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?

Coverage is only 40%, so the description must compensate, and it does for the most complex parameter: entries is explained as an ordered list where each item is a diagram id plus a scannable scenario name plus a Markdown note, and id is tied to update-vs-create. It adds the critical 'replaces the whole ordered list' semantics the schema omits, though visibility and title remain unexplained.

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?

States a specific verb+resource with precise upsert semantics: 'Create a collection, or with id update one.' This distinguishes it from get_collection and list_collections, and the wholesale-replacement clause implicitly separates it from add_to_collection. It stops short of naming that closest sibling outright.

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?

It says when to create vs update via the id, and 'entries replaces the whole ordered list' implies append-style tools are the alternative. But add_to_collection is never named, so the agent must infer the choice between adding one entry and rewriting the list.

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