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

The readOnlyHint annotation already establishes that this is a safe read operation. The description adds the REST endpoint and selection modes, but does not disclose pagination behavior, auth requirements, rate limits, or return format beyond what the schema implies.

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 tightly written sentences with the core purpose and scope front-loaded. The endpoint reference is compact and useful with no wasted words.

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 low-complexity, read-only data fetch with 100% schema coverage and a readOnlyHint annotation, the description covers the essential selection behavior. No output schema exists, but the return type (battery readings) is self-evident enough that this is nearly complete.

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 coverage is 100%, so all five parameters are documented in the schema. The description echoes the range/latest distinction but adds no syntax, format, or interaction details beyond what the schema already provides, making the baseline 3 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?

States a specific verb ('Fetch') and resource ('ring battery readings'), with the scope of a DATETIME range or latest reading. The resource clearly distinguishes it from siblings like oura_get_heartrate or oura_get_personal_info.

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 phrase 'over a DATETIME range, or just the latest' gives clear context for choosing between the two retrieval modes. It stops short of naming exclusions or alternatives, but for a simple read tool this is adequate guidance.

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