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

Annotations already declare readOnlyHint=false, destructiveHint=false and idempotentHint=true, so the safety profile is covered. The description adds real value beyond that with the precondition that the customer must already exist as a contact, though it omits failure behavior and whether the operation can be undone.

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?

Front-loaded with the action and only two sentences long. The inline visibility gloss is somewhat redundant with the enum descriptions and slightly bloats the sentence, but nothing is wasted overall.

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 6-parameter mutation with no output schema, the description covers purpose and one precondition but leaves gaps: no precedence rule when both owner_email and owner_contact_id are supplied, and no statement of what is returned or how a bad contact id surfaces.

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 100%, so baseline is 3. The description does add one nuance the schema does not state plainly – that owner assignment and visibility setting are independent and combinable ("and/or") – but the visibility enum meanings it spells out are verbatim duplicates of the schema description.

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 and resource ("Assign a collection record") plus the two effects it has: ownership and visibility. It is distinguishable from neighbors like update_collection_item, but it never names an alternative, so the agent has to infer the boundary itself.

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 prerequisite "The customer must already be a contact on this site" is a genuine usage constraint. However, there is no guidance on when to choose this over update_collection_item or set_collection_item_display, nor on what to do when the contact does not yet exist.

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