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

Annotations only say readOnly=false, destructive=false, openWorld=true, idempotent=false; the description adds material detail beyond those: external X provider reads may be billed, no Creative Credits are consumed, and nothing gets published as a side effect. The billing/cost disclosure is exactly the kind of operational fact annotations cannot convey.

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 short sentences, front-loaded with the action and scope, followed by the cost warning and the routing hint. Every sentence carries distinct information with no restatement of the title.

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?

Covers action, cost, side effects, and the sibling alternative, which is sufficient for a 3-parameter mutation-adjacent tool. It does not describe what the refreshed metrics look like or how freshness is reported, and no output schema exists to fill that 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 100%, with post_id and brand_id already documenting their provenance (get_calendar, list_brands), so baseline is 3. The description reinforces that post_id must be a single published post but adds no syntax or format detail beyond 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?

States a specific verb (refresh) and resource (performance metrics for ONE published post), with the cardinality constraint in caps to prevent misuse. It explicitly names the sibling get_post_performance as the alternative, so an agent can distinguish the two without opening either schema.

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?

"Use get_post_performance for ordinary reporting" gives an explicit alternative and the condition that selects it. "Review before approving" signals this is a deliberate, cost-bearing action rather than a routine call, though it stops short of stating precise when-not conditions (e.g., staleness thresholds).

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