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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description still adds real value by disclosing workspace scoping and the miss semantics ("Returns null when no such event is visible to the caller"), telling the agent it gets null rather than an error on a bad or invisible id.

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 scoped resource, then the safety note, then the return edge case. "Read-only" mildly duplicates the annotation but is cheap and no sentence is wasted.

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 getter with no output schema, the description supplies the two things an agent most needs: workspace scoping and null-on-miss behavior. The only meaningful omission is any hint about id provenance or accepted format.

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 0%, so the description must carry the weight for event_id, and it only restates "by id" without explaining format, where the id comes from, or that both integer and string forms are accepted (visible only in the schema type union). It adds essentially nothing 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 and resource ("Read a single calendar event") plus the lookup key ("by id"), which cleanly separates it from create_event, update_event, and delete_event. It stops short of naming any sibling explicitly, so it lands at clear-but-not-differentiated-by-reference.

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 "by id" implies the tool is for callers who already hold an identifier, and "from the caller's workspace" scopes the lookup. There is no explicit statement of when to prefer this over a search or listing tool, and no exclusions.

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