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

Annotations already establish that this is a non-readonly, non-destructive, non-idempotent, closed-world mutation. The description adds meaningful behavioral context beyond that: it links readings to the running fast, notes GKI derivation, and discloses mirroring to Vora, although it does not discuss auth or response behavior.

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 compact sentences front-load the core action and immediately follow with the key constraint. There is no redundant restatement of schema or annotations.

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 seven-parameter mutation tool with annotations and no output schema, the description covers purpose, key side effects, and the at-least-one glucose/ketone requirement. It leaves some gaps around when to choose this over related biomarker tools and full parameter semantics, but it is largely sufficient for correct invocation.

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 covers 57% of parameters, with descriptions for measuredAt, glucoseUnit, minutesSinceMeal, and measurementContext. The description contributes the important cross-parameter rule that at least one of glucose or ketone is required, but it does not add meaning for the remaining undocumented fields such as note, glucoseValue, or ketoneMmol.

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: recording a glucose and/or ketone reading in Still. It adds useful scope details such as linking to the running fast, deriving GKI, and mirroring to Vora, which helps distinguish it from generic biomarker tools, though it does not explicitly name a sibling alternative.

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?

Usage context is implied through the Still-specific framing and the note that readings are mirrored to Vora, but there is no explicit when-to-use versus when-not-to-use guidance. The only concrete rule given is the operational constraint that at least one of glucose or ketone must be supplied.

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