Nightscout MCP Server

compare_periods

Compare glucose statistics between two periods, showing time-in-range, average, SD, CV, and HbA1c deltas to evaluate training effects, medication changes, or daily patterns.

Instructions

Compare glucose statistics between two time periods side by side. Use for: training vs rest days, this week vs last week, before vs after medication changes, weekdays vs weekends. Returns TIR, average, SD, CV, HbA1c, and time-in-ranges for both periods with deltas.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "periodA_from": "<periodA_from>",
      "periodA_to": "<periodA_to>",
      "periodB_from": "<periodB_from>",
      "periodB_to": "<periodB_to>"
    },
    "name": "compare_periods"
  }
}

Input Schema

Name	Required	Description
`labelA`	No	Label for period A (e.g., 'Training days')
`labelB`	No	Label for period B (e.g., 'Rest days')
`periodA_to`	Yes	Period A end date (ISO 8601 or YYYY-MM-DD)
`periodB_to`	Yes	Period B end date (ISO 8601 or YYYY-MM-DD)
`periodA_from`	Yes	Period A start date (ISO 8601 or YYYY-MM-DD)
`periodB_from`	Yes	Period B start date (ISO 8601 or YYYY-MM-DD)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.4.0Sep 6, 2026

TDQS

A3.8/5.0

Behavior3/5

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

The description states what the call returns (TIR, average, SD, CV, HbA1c, time-in-ranges, deltas), which is behaviorally useful. However, with no annotations, it omits any statement about side effects (even read-only), period handling, or data requirements, leaving some behavioral aspects to inference.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, front-loaded with the core action, then usage contexts, then return values. No repetition or filler; every segment adds information and the structure is easy to scan.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with no output schema and no annotations, the description covers the core purpose, when to use it, and what will be returned. It leaves minor gaps like date inclusivity and overlapping periods, but the schema covers parameter formats and the return list is explicit.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema already describes all six parameters with 100% coverage, so the baseline is 3. The description does not add parameter-level detail beyond the schema, though it does set expectations for what the parameters are used for by describing the comparison output.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb ('Compare') and resource ('glucose statistics between two time periods side by side'), making the tool's function immediately clear. It does not explicitly name a sibling tool such as weekly_comparison to differentiate from, though the use-case list helps distinguish it from single-period tools like get_statistics.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The 'Use for:' clause gives concrete scenarios (training vs rest days, this week vs last week, medication changes, weekdays vs weekends), providing clear context for when the tool is appropriate. It does not mention when not to use it or point to alternatives, so exclusion guidance is missing.

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