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

The annotations already cover the behavioral profile: readOnly=false, idempotent=true, destructive=false, and openWorld=false. The description adds no behavior beyond that; it does not say whether completion records a timestamp, whether it can be undone, or what happens when the action is already done. Given the rich annotation set, a 3 is appropriate, but this description is not a strong example of added context.

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?

Two short sentences with zero filler. The action purpose is front-loaded, and the identifier-discovery hint follows immediately.

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 single-parameter mutation with an output schema and a full annotation set, the description covers what is needed to select and call the tool. The only shortfall is that it does not explain the irreversibility or the post-condition of marking an action done.

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 would be 3. The description nonetheless adds real value beyond the schema's bare "The action to complete" by naming the two concrete sources for action_id (get_person relationship.actions and list_actions). That provenance guidance is not in the schema.

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 and resource: "Mark a follow-up / action done". This clearly distinguishes the tool from create_action, delete_action, and update_action, which all operate on the same resource. It stops short of an explicit contrast with update_action, but the intent is unambiguous.

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 usage guidance is limited to telling the agent where to obtain the action_id, via get_person (relationship.actions) or list_actions. This is practical help with the prerequisite. However, it does not say when to use this tool instead of update_action, or whether the action can be marked done only once.

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