MyFitnessPal MCP Server

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mfp_log_fast

Record a completed intermittent fasting window in MyFitnessPal by specifying start and end times. The tool creates an entry and returns an ID for later updates or deletions.

Instructions

Log a completed intermittent fasting window in MyFitnessPal.

Creates a new entry with the given start and end times. If `id` is
omitted, a fresh uppercase UUIDv4 is generated (matches how the iOS
app self-assigns ids). The returned `id` is what `mfp_update_fast` and
`mfp_delete_fast` accept — save it if you plan to modify the entry
later.

Args:
    params: LogFastInput (fast_started, fast_ended, id?, response_format)

Returns:
    str: The created entry with id, timestamps, created_at, and status

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": {
      "params": "<params>"
    },
    "name": "mfp_log_fast"
  }
}

Input Schema

Name	Required	Description	Default
`params`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 13, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Annotations indicate a write operation (readOnlyHint=false) and non-idempotency (idempotentHint=false). The description adds behavioral details beyond these annotations: it states a new entry is created, explains the UUID generation behavior (matches iOS conventions), and reveals the return structure. It does not contradict annotations and provides useful context about id handling and output format.

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?

The description is concise and well-structured: a clear purpose sentence, a behavioral note about id and future modification, then an Args/Returns block. Every sentence serves a purpose, and the most important information (what it does and the id contract) is front-loaded. No fluff or unnecessary detail.

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 straightforward create operation, the description covers the essential points: action, id handling, and return format. It doesn't mention error conditions or prerequisites (e.g., authentication), but the annotations and schema cover the safety and parameter constraints. Given the tool's simplicity, this is adequately complete.

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

Parameters2/5

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

The description lists parameter names (fast_started, fast_ended, id?, response_format) but provides no substantive semantic details beyond what the schema already contains. The schema itself has rich descriptions for each parameter (e.g., ISO 8601 format, UUID pattern, required ordering). Since schema description coverage is 0% per the signal, the description was expected to compensate, but it does not meaningfully add to parameter understanding—only the id generation note, which is also in the schema.

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

Purpose5/5

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

The description opens with a clear action: 'Log a completed intermittent fasting window in MyFitnessPal.' It specifies the verb (log), the resource (intermittent fasting window), and the system (MyFitnessPal). It also mentions creating a new entry and explicitly notes that the returned id is used by mfp_update_fast and mfp_delete_fast, distinguishing this tool from its sibling update/delete tools.

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 description implies when to use this tool (to log a new completed fast) and provides a clear link to the update/delete tools by stating the returned id is what those tools accept. However, it does not explicitly contrast with alternatives like mfp_log_meal or state conditions for choosing this over them, so it is clear but not fully explicit.

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