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

Annotations already indicate readOnlyHint=false and destructiveHint=false. The description adds that Blocks computes load_au = sRPE × duration_min and that the activity must be completed, which is meaningful behavioral context beyond the annotations. It does not discuss idempotency or overwrite behavior, but given annotation coverage this is adequate.

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?

The description is two sentences with no filler. The first sentence front-loads the action and target; the second adds the computation formula and universality context. Slightly dense but every clause earns its place.

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 tool with no output schema, the description covers the essential calling context: what to provide, where the activity comes from, and the system's resulting computation. It does not describe return values or error cases, but that is not expected given the low complexity and annotation coverage.

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?

With 0% schema description coverage, the description fully compensates: it explains srpe is Borg CR-10 (0-10) and should be recorded ~30 min post-session, and that activity_id refers to a completed activity from list_activities. This adds real meaning to otherwise bare schema fields.

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 ('Attach'), a resource ('session RPE'), and a target ('completed activity from list_activities'), and it gives the Borg CR-10 scale and the computed load_au formula. This clearly separates it from generic log_metric or log_lactate siblings.

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?

It explicitly says the activity must come from list_activities and be completed, and notes the ~30 min post-session timing. It also frames when to use it (any sport without a power meter, as universal load currency alongside TSS), though it does not directly name alternative tools or state exclusions.

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