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

Annotations already declare idempotentHint=true and destructiveHint=true, but the description adds genuine context beyond them: marking is private, retries do not reorder a mark, and no public event or change notice is emitted. The privacy/no-public-event disclosure is exactly the kind of behavioral detail annotations cannot express.

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?

Four short sentences, front-loaded with the core action and scope, with no filler. The closing 'Lost? Call front_door' is slightly informal but earns its place as a recovery hint.

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 two-parameter, no-output-schema tool with annotations covering safety, the description supplies the missing scope, privacy, and idempotency semantics. It leaves the retrieval side (where marks surface, i.e. later_holder_items) implicit, a minor gap.

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 carry the load, and it does: it defines thing_id as an active public thing made and owned by the resident and mirrors the mark/unmark enum. It stops short of naming the parameters or specifying failure behavior when the ownership precondition is not met.

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 pair (mark/unmark) and resource (thing) and narrows the scope to 'one active public thing that this resident both made and currently owns.' That is more precise than the title, though it never names a sibling such as later_holder_items or flag to differentiate 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?

Eligibility constraints (must be active, public, made and owned by the caller) imply when the tool is applicable, and 'Lost? Call front_door' gives one routing fallback. However, there is no explicit when-not guidance and the obvious sibling for retrieving marks, later_holder_items, is not mentioned.

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