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

With no annotations, the description fully discloses important behaviors: it explains that missing records mean no measurement, not insufficient sun, and states the OAuth scope requirement. It also mentions the calendar rendering behavior. This goes well beyond what structured annotations would provide.

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 compact, with four sentences covering key aspects (what it returns, date coverage, missing-data caveat, auth). It is front-loaded, but the 'from'/to' inconsistency is a structural flaw that prevents a perfect score.

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?

The description covers the main data points returned, the missing-data semantics, and auth. However, without an output schema, it leaves the exact return structure ambiguous, and the 'from'/'to' reference conflicts with the actual parameter. It is reasonably complete for a simple tool but has notable gaps.

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 description references 'from' and 'to' parameters, but the schema only defines a 'days' parameter. This is contradictory and confusing, detracting from the schema's own clear description of 'days'. The description adds no value here and actually introduces inconsistency.

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 clearly states the tool retrieves the signed-in user's sun history from the app's calendar, including viable sun days, confirmed going-outside days, and current streak. It distinguishes this from siblings like get_sun_forecast (future) and get_current_status (current) by explicitly focusing on historical calendar data.

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 description provides context on when this tool is relevant (for signed-in users' history) and highlights a key caveat about missing records, but it does not explicitly name alternatives or say when not to use it. The usage is implied rather than clearly differentiated from sibling tools.

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