fix: reorder variation variable union types and improve MCP descriptions for correct JSON typing

[jonathannorris]

Summary

• Reorder Zod union types for variation variables to put boolean and number before string across all 5 variation schemas
• Add explicit descriptions to MCP tool schemas telling AI models to use native JSON types for variable values

Motivation

Users reported that creating/updating features with boolean variation variables via MCP fails with:

Expected type of value for variable to be Boolean, but received String

The root cause is that AI models send "true" (string) instead of true (boolean) when calling the MCP tools. No serialization bug exists in our code — the issue is AI model behavior. Our Zod validation accepts "true" because z.string() matches before z.boolean() is tried, so the error only surfaces when the DevCycle API rejects the request.

Changes

src/api/zodSchemas.ts — Reordered union from [string, number, boolean, ...] to [boolean, number, string, ...] in CreateVariationDto, Variation, UpdateVariationDto, FeatureVariationDto, and UpdateFeatureVariationDto. This changes the anyOf order in the advertised JSON Schema. It's a loose theory that having string first in anyOf influences models to default to string encoding — worth trying but not guaranteed to fix the issue on its own.

src/mcp/types.ts — Enhanced descriptions on CreateFeatureArgsSchema.variations, UpdateFeatureArgsSchema.variations, and the shared variablesDescription used by standalone variation tools. Descriptions now explicitly state to use native JSON types with examples. This is likely the more impactful change since models tend to follow explicit instructions in tool descriptions.

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Status	Name	Latest Commit	Updated (UTC)
✅ Deployment successful! View logs	devcycle-mcp-server	33c2e65	Mar 12 2026, 07:53 PM

[Copilot]

Pull request overview

This PR adjusts the advertised JSON Schema / MCP tool documentation for variation variables to better steer MCP tool callers toward using native JSON booleans/numbers (instead of string-encoding), addressing user-reported failures when the DevCycle API expects typed variable values.

Changes:

• Reorders the Zod union member ordering for variation variables across multiple variation DTOs (to change anyOf ordering in generated JSON Schema).
• Expands MCP tool argument descriptions to explicitly instruct using native JSON types (with examples) when populating variation variables.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/mcp/types.ts	Updates tool argument descriptions for variations/variables to explicitly request native JSON typing and provide examples.
src/api/zodSchemas.ts	Reorders union type members for variation variables to prioritize boolean/number before string in generated schema output.

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