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

With no annotations provided, the description carries the full burden of explaining behavior. It states that the tool records a delivery and is used for analytics, which implies a state change, but it does not disclose whether the action is idempotent, whether it mutates the original event, or what happens if the event_id does not exist. This is adequate for a simple tool but not fully transparent.

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?

The description is two short sentences with no filler. The core purpose is front-loaded in the first sentence, and the second sentence adds useful analytics context without drifting. It is appropriately sized for a tool with one parameter.

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 deliberately simple tool, the description gives the essential behavior and purpose. However, it lacks guidance on event_id provenance, expected error cases, and whether duplicate marking is allowed or harmful. Given no output schema and no annotations, a little more context would make the tool fully safe to invoke.

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?

The schema provides only an opaque event_id string with no description, and the schema description coverage is 0%. The description mentions 'capability event' but does not explain how to obtain event_id, its expected format, or its lifecycle context. The tool description needs to compensate for the schema gap but does not.

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 uses a specific verb ('Mark') and a clear resource ('a capability event') and states the operational outcome ('as delivered to the calling subscriber'). It is immediately distinguishable from the sibling retrieval tools, which are about getting, listing, and searching capabilities.

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 phrase 'delivered to the calling subscriber' clearly indicates the tool should be used after the subscriber has received the event, distinguishing it from read-only capabilities exploration. It does not explicitly name alternatives or state when not to use it, but the context is strong enough that an agent can infer the intended moment of use.

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