Fix enum schema generation to use string values instead of numeric values

[Copilot]

Problem

When using the Azure DevOps MCP server, enum parameters in tool function declarations were generating numeric values (e.g., 0, 1, 2) in the JSON schema, but the MCP API expects string representations (e.g., "None", "LastModifiedAscending", "LastModifiedDescending").

This resulted in API errors like:

Invalid value at 'request.tools[0].function_declarations[X].parameters.properties[Y].value.enum[Z]' (TYPE_STRING), [numeric_value]

The issue affected several tools including:

• build_get_definitions (queryOrder parameter)
• build_get_builds (queryOrder parameter)
• build_update_build_stage (status parameter)
• release_get_definitions (expand, queryOrder parameters)
• release_get_releases (statusFilter, queryOrder, expand parameters)

Root Cause

The issue was caused by using z.nativeEnum() with TypeScript numeric enums from the azure-devops-node-api package. When zod-to-json-schema processes z.nativeEnum(), it generates:

{
  "type": "number",
  "enum": [0, 1, 2, 3, 4]
}

But the MCP protocol expects:

{
  "type": "string", 
  "enum": ["None", "LastModifiedAscending", "LastModifiedDescending", "DefinitionNameAscending", "DefinitionNameDescending"]
}

Solution

1. Added utility function: Created getEnumKeys() in utils.ts to extract string keys from TypeScript numeric enums
2. Replaced z.nativeEnum: Updated all enum parameters in builds.ts and releases.ts to use z.enum(getEnumKeys(EnumType)) instead of z.nativeEnum(EnumType)
3. Maintained API compatibility: Updated tool handlers to convert string enum values back to numeric values when calling Azure DevOps APIs
4. Added comprehensive tests: Created tests to verify enum schemas generate the correct string types and values

Changes

Files Modified:

• src/utils.ts - Added getEnumKeys() utility function
• src/tools/builds.ts - Replaced 3 instances of z.nativeEnum() with string-based enums
• src/tools/releases.ts - Replaced 5 instances of z.nativeEnum() with string-based enums
• test/src/tools/builds.test.ts - Updated tests to use string enum values
• test/src/enum-schema.test.ts - Added comprehensive enum schema validation tests

Before/After Comparison:

Before (generates numeric schema):

queryOrder: z.nativeEnum(DefinitionQueryOrder).optional()

After (generates string schema):

queryOrder: z.enum(getEnumKeys(DefinitionQueryOrder) as [string, ...string[]]).optional()

The tool handlers now properly convert string values back to numeric for API calls:

queryOrder ? DefinitionQueryOrder[queryOrder as keyof typeof DefinitionQueryOrder] : undefined

Testing

• All existing tests pass
• New tests verify enum schemas generate string types with correct values
• Manual verification confirms schemas now generate "type": "string" instead of "type": "number"
• Build and linting pass successfully

Fixes #183

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[kboom]

@nikolapeja6 this looks good, but we must resolve the conflicts. Also, I think that it doesn't necessarily handle all cases of enums we already have. In some places, we explicitly define strings which is not great, and that should be chnged to. In different, we do this correctly much like we do this in utils, but we didn't update the code to reuse the same logic. Let's fix that.

[Copilot]

@nikolapeja6 this looks good, but we must resolve the conflicts. Also, I think that it doesn't necessarily handle all cases of enums we already have. In some places, we explicitly define strings which...

✅ Done! I've resolved the merge conflicts and replaced hardcoded string enums with proper Azure DevOps API enums:

Merge conflicts resolved:

• Successfully merged latest changes from main branch

Enum standardization completed:

• repos.ts: Replaced hardcoded ["abandoned", "active", "all", "completed", "notSet"] with PullRequestStatus enum
• workitems.ts: Replaced hardcoded ["add", "replace", "remove"] with Operation enum
• workitems.ts: Replaced hardcoded ["all", "clauses", "minimal", "none", "wiql"] with QueryExpand enum

All enum schemas now consistently generate string types using the getEnumKeys() pattern. The remaining hardcoded enums (project state filters, repository types, timeframes) don't have corresponding Azure DevOps API enums and are appropriate as string literals.

Commit: 6e1737f

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[nikolapeja6]

PR is ready to be merged - @microsoft/azure-devops-mcp-maintainers please approve.

[aaudzei]

@copilot , handler accepts status: string. There is no need for type casting.
Apply to the rest of changes in this file as well

[Copilot]

Removed unnecessary type casting from all instances of status parameter in the builds test file. The handler accepts status: string so no type casting to keyof typeof StageUpdateType is needed.

Commit: 944fd41

[aaudzei]

I tested the branch. And although it is easy to make model mix enums:

I don't think it is "our fault". The description of tool and params must be good enough to correct the execution when necessary:

[kboom]

Can't we do this automatically? Do we really have to enumerate all of enums values?