Garmin MCP Server

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set_heart_rate_zones

Configure heart-rate training zones for a chosen sport on Garmin Connect, preserving omitted values and returning the saved configuration.

Instructions

Set an account-level heart-rate training-zone configuration for one sport.

WARNING: This mutates the user's Garmin Connect account configuration. Garmin stores zones per sport, so DEFAULT (the generic fallback), RUNNING, CYCLING, and other sport profiles are independent. Only the requested sport is written; omitted values are read from that sport's current configuration and preserved.

This change affects future activity recording and zone-based training. It does NOT retroactively re-slice already-recorded activities: their heart-rate zone boundaries were baked in when those activities were recorded.

The calculation method may be max_hr (% maximum heart rate), hrr or karvonen (% heart-rate reserve), lthr (% lactate-threshold heart rate), or custom_bpm. Manual zone_boundaries are only accepted with the custom_bpm method. Garmin's API does not persist a separate CUSTOM enum: direct-BPM zones are sent and read back with trainingMethod=HR_MAX while the explicit zone floors remain authoritative.

The tool performs a read-modify-write and then re-fetches the requested sport. Its result is the configuration Garmin actually saved, not the request payload.

Args: sport: Garmin sport key, e.g. default/generic, running, or cycling. max_hr: Maximum heart rate in BPM. resting_hr: Resting heart rate in BPM. Supplying it disables Garmin's resting-HR auto-update for this zone profile. lactate_threshold_hr: Lactate-threshold heart rate (LTHR) in BPM. calculation_method: max_hr, hrr/karvonen, lthr, or custom_bpm. zone_boundaries: Five strictly increasing BPM floors [Z1, Z2, Z3, Z4, Z5]. Every floor must be at most max_hr.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`sport`	Yes
`max_hr`	No
`resting_hr`	No
`zone_boundaries`	No
`calculation_method`	No
`lactate_threshold_hr`	No

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 7, 2026

TDQS

A4.8/5.0

Behavior5/5

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

With no annotations provided, the description fully discloses the mutating nature ('WARNING: This mutates the user's Garmin account configuration'), the read-modify-write strategy, side effects like disabling resting-HR auto-update, and that the returned value is the actual saved configuration.

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 lengthy but appropriately structured with a warning, effect explanation, and a clear Args list. Every sentence adds necessary information for safely using this mutating tool, and the format makes it easy to scan.

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

Completeness5/5

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

The description covers all critical aspects for correct invocation: required sport, optional parameters and their semantics, calculation method variants, zone boundary validation, side effects, and the meaning of the return value. This is sufficient for an agent to use the tool without external documentation.

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

Parameters5/5

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

Although the schema has no descriptions, the Args section explains every parameter, including allowed values (e.g., calculation_method options), constraints (five strictly increasing zone boundaries), and interactions (resting_hr disables auto-update). This fully compensates for the 0% schema description coverage.

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 clearly states the tool's function: 'Set an account-level heart-rate training-zone configuration for one sport.' This is a specific verb and resource, and it is distinct from sibling tools like get_heart_rate_zones.

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 provides rich usage context, including read-modify-write behavior, per-sport persistence, and the non-retroactive effect on already-recorded activities. It does not explicitly mention when to use this tool over an alternative, but there is no direct sibling setter, making the guidance effectively clear.

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

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