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

Annotations already declare the safety profile (readOnly=false, destructive=false, idempotent=true), so the description's added value is the patch semantics and the hard restriction that Rawa-curated events are immutable. "Free" also discloses that the call consumes no credits, a non-obvious cost trait not present in any structured field. It does not describe what a partial update returns or whether omitted fields are preserved vs. cleared, which keeps it below 5.

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 action and scope, then the update contract, then the exclusion, then cost. The "Free." fragment is terse but carries real information about credit consumption, so it earns its place.

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?

The tool has an output schema and annotations, so return values and safety are covered elsewhere; the description fills in the two gaps an agent would otherwise trip on — partial-update semantics and the curated-event restriction. Only the treatment of cleared vs. preserved fields is left implicit.

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?

With 71% schema description coverage, the schema already documents date, endDate, eventId, brandId, and markets. The description adds the crucial implication that all non-eventId fields are optional and only changed fields need sending, but it says nothing about title, description, or markets semantics. Baseline 3 is appropriate given the schema carries most of the load.

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?

"Change one of the brand's own calendar events" states a specific verb and resource and immediately bounds the object set to brand-owned events. That scoping cleanly separates it from create_calendar_event, delete_calendar_event, and list_calendar_events without the agent needing to open a 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?

"Pass only the fields to change" tells the agent this is a partial-update operation, and the Rawa-curated exclusion states a concrete when-not condition. It stops short of naming a sibling to use for the curated case (there isn't one) or for creating events, so it is clear but not fully routed.

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