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

Annotations already declare destructive=false? No -- they declare destructiveHint=true, idempotentHint=true, readOnlyHint=false, so the safety profile is partly covered. The description adds real behavior beyond that: partial updates are supported (omit the field you don't want to touch) and both fields are required before publishing, with set_activity_content reporting empties. It doesn't explain what 'destructive' means here (overwriting an existing title) or permission requirements, so it's not complete.

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, zero filler, with the core action ('send only what you want to change') and the publish precondition front-loaded. Every sentence carries distinct information rather than repeating the name or schema.

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 4-parameter mutation tool with no output schema, the description covers the partial-update contract, the publish precondition, and sibling boundaries, which is most of what an agent needs. It leaves the destructive/idempotent implications of overwriting an existing value and any authorization requirement unstated, so it is strong but not exhaustive.

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%, including a detailed intent enum explaining fill_empty vs user_asked, so the schema carries nearly all parameter meaning. The description's 'send only the one you want to change' restates optionality already implied by the schema and adds little syntax or format detail. Baseline 3 applies when the schema does the heavy lifting.

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 ('Update the title and the description of an activity') and immediately scopes it away from related siblings ('The audience and the visibility have their own tools'), which separates it from set_activity_audience and set_activity_privacy in the sibling list. An agent can identify the tool without opening the 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?

Gives concrete usage context: 'Send only the one you want to change,' plus the precondition that both fields are needed for publishing and that set_activity_content surfaces missing values in next_step. It routes audience/visibility work to other tools. It stops short of an explicit when-not rule (e.g., when to prefer set_activity_content over this tool), so it's clear context without full exclusions.

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