get_night

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

With no annotations, the description carries the behavioral burden and does well: it discloses the returned metrics, the ready-made text format, the meaning of target_date, and the additive behavior of history_days. It does not explicitly state read-only/no-side-effect behavior or describe missing-data handling, but the read-oriented nature is strongly implied by 'get' and 'measured'.

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 dense but well structured: it front-loads what data is returned, then explains date semantics, history behavior, and the instruction to quote numbers as-is. Every sentence adds useful information, with no filler.

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 two-parameter read tool with an output schema, the description is largely complete: it covers the returned metrics, both parameters, defaults, and history behavior. Minor gaps remain around no-data cases and timezone assumptions, but nothing critical to correct invocation is missing.

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 description coverage is 0%, so the description must compensate, and it does: target_date is explained as YYYY-MM-DD for the wake-up day with 'last night' as today's default, and history_days is constrained to 0-13 with per-night line behavior. This adds substantial meaning beyond the bare schema.

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 identifies the resource and contents: one night of Eight Sleep mattress data returned as ready-made text, including sleep score, stages, HRV, heart rate, respiratory rate, and temperatures. It lacks an explicit retrieval verb, but the intended purpose is still easy to infer. There are no sibling tools to differentiate from.

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 gives concrete usage guidance for both parameters: target_date is the wake-up day and defaults to today for last night, while history_days adds earlier-night lines. It does not provide explicit when-not-to-use guidance or alternatives, but no alternatives are present and the key interpretation rules are covered.

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