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

Beyond the annotations (readOnlyHint=false), the description discloses that samples are appended by default, replace:true overwrites the entire set, and samples become visible as markers retrievable via get_activity. This gives the agent a concrete model of side effects and resulting state.

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?

Purpose is front-loaded and every sentence carries distinct functional information: scope, parameter semantics, append/overwrite behavior, and downstream effects. It is dense but not bloated; no filler or restatement of schema constraints.

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 3-parameter logging tool with no output schema, it covers input semantics, mode of operation, downstream retrieval, and scope limitations. An agent can confidently construct a correct call without needing additional tools; activity_id is self-explanatory.

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?

The schema has no property descriptions (0% coverage), so the description carries full weight. It defines t as seconds on the MOVING clock with estimation guidance, mmol as the reading, and explains the replace flag's default behavior. This is meaningful semantic coverage for all three parameters.

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 opens with a specific verb ('Record') and a precise resource ('athlete's blood-lactate samples on a completed activity'), reinforced with a concrete example. It clearly distinguishes log_lactate from sibling log_* tools by naming blood-lactate as the metric and 'completed activity' as the target.

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?

Provides explicit context: use on completed activities, append by default vs replace:true, and a clear when-not instruction ('put your interpretation in set_activity_notes, not here'). It does not explicitly contrast with log_metric or log_session_rpe, but the boundary is clear enough for correct selection.

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