add_activity_message

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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond the annotations: nothing is replaced, blank text is refused, the message id is returned, and dry_run shows the request without writing.

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 sentences are front-loaded with the usage condition, then the mutation behavior, then the read alternative. Every sentence earns its place with no redundancy or filler.

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?

There is no output schema, and the description adequately states the return value: the message id, with dry_run returning the request instead. Combined with annotations and full schema coverage, an agent has what it needs to call the tool correctly.

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%, so the schema already documents content, dry_run, and activity_id. The description repeats that blank text is refused and that dry_run shows the request, but adds no new syntax or meaning beyond the schema descriptions. Baseline 3 is appropriate.

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 states a specific verb and resource: it adds one message to an activity's thread on Intervals.icu. It also distinguishes the tool from get_activity_messages by telling the agent to use that sibling to read the thread. This is enough for an agent to 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?

The first sentence sets a clear condition: use only when the athlete asks to post a note or comment on an activity. The final sentence names get_activity_messages as the alternative for reading the thread. Both when-to-use and a relevant alternative are explicit.

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