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

Annotations already declare destructiveHint=true, idempotentHint=true, and readOnlyHint=false, so the description's main added value is the precondition that no sessions may be assigned. That is genuinely useful failure-mode context, but it does not say what happens to the response, whether the deletion is recoverable, or what error surfaces when sessions exist.

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 no filler, and the constraint is stated immediately after the purpose. Nothing is wasted, though the phrasing 'from the provided event' is slightly redundant with the event_id 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 two-parameter destructive delete, the essential operational fact – the no-sessions precondition – is present, annotations carry the safety profile, and an output schema exists to explain returns. What is missing is minor: no note on how the agent should verify the precondition beforehand.

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%: event_id (UUID returned by search_events) and category_id (UUID) are already documented. The description adds no further semantics about either parameter, so the baseline 3 applies.

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 names a specific verb and resource ('Delete a session category') and scopes it to 'the provided event', which separates it from update_session_category and create_session_categories. It stops short of explicitly naming those siblings, so it is clear but not maximally differentiated.

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 precondition 'can only be deleted if no sessions are assigned' is real usage guidance, but it is a hard constraint rather than a when-to-use rule. No alternative is named (e.g., what to do instead if the category still has sessions, or whether delete_session is needed first).

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