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

Annotations declare readOnlyHint=false, destructiveHint=false, and openWorldHint=true, so the mutation/safety profile is already covered. The description adds one genuinely useful behavioral fact not in the annotations – 'Resolves to null on success' – which matters because there is no output schema, but it omits whether an existing description is overwritten and what happens on failure.

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, action first, return-value behavior second. Nothing is padded and both clauses carry information.

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 simple two-parameter mutation with no output schema, the 'null on success' note and the annotations cover the essentials. But with the description parameter undocumented in both schema and prose, and no error/prerequisite behavior stated, it is only minimally complete.

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 coverage is only 50%: the 'description' parameter has no schema description at all, and the 'activityId' doc ('Numeric id') is slightly at odds with a type union of integer|string. The description text adds no parameter guidance to compensate for the gap.

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 ('Sets an activity's description'), so the operation is unambiguous. However, it does nothing to distinguish itself from near-identical siblings like set_activity_name, set_activity_feel, set_activity_type, or set_activity_perceived_effort.

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 description gives no when-to-use context, no prerequisites (e.g. the activity must exist), and no mention of alternative tools. An agent must infer that this is the write-side counterpart to get_activity_details.

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