create_iteration_field and add_iteration fail with GraphQL input-type errors #21

Summary

Both iteration-creation tools fail against the live GitHub GraphQL API. The underlying updateProjectV2Field mutation works fine when called directly — the server appears to be sending the iteration list under a wrong/nonexistent input-type name.

Repro

Called create_iteration_field against a fresh ProjectsV2:

{
  "projectId": "PVT_kwHOAwJiCM4BUd_L",
  "fieldName": "Sprint",
  "duration": 1,
  "startDate": "2026-04-13",
  "iterations": [
    { "title": "M1 — Foundations",          "startDate": "2026-04-13", "duration": 1 },
    { "title": "M2 — Learned SR backbone",  "startDate": "2026-04-14", "duration": 1 },
    { "title": "M3 — Production features",  "startDate": "2026-04-15", "duration": 1 },
    { "title": "M4 — Polish & v0.1.0",      "startDate": "2026-04-16", "duration": 1 }
  ]
}

Error

ProjectV2IterationFieldConfigurationIterationInput isn't a defined input type (on $iterations)

Side effect: the iteration field itself was still created (empty). A follow-up create_iteration_field with the same fieldName then fails with Name has already been taken.

Calling add_iteration on the empty field also fails:

Field 'startDate' doesn't exist on type 'ProjectV2IterationFieldConfiguration'

What works

Direct GraphQL via gh api graphql succeeds with this shape:

mutation {
  updateProjectV2Field(input: {
    fieldId: "PVTIF_…",
    iterationConfiguration: {
      startDate: "2026-04-13",
      duration: 1,
      iterations: [
        { title: "M1 — Foundations",         startDate: "2026-04-13", duration: 1 },
        { title: "M2 — Learned SR backbone", startDate: "2026-04-14", duration: 1 }
      ]
    }
  }) {
    projectV2Field {
      ... on ProjectV2IterationField {
        id
        configuration { iterations { id title startDate duration } }
      }
    }
  }
}

Returns ProjectV2IterationField with populated configuration.iterations (ids, titles, dates).

Schema notes

Introspection confirms:

• UpdateProjectV2FieldInput.iterationConfiguration → ProjectV2IterationFieldConfigurationInput (non-deprecated, public).
• ProjectV2IterationFieldConfigurationInput has three non-null fields: startDate: Date!, duration: Int!, iterations: [<unknown>]!.
• The list element type is not publicly named — searching the schema for any *Iteration*Input returns nothing. In practice GitHub accepts literal objects with { title, startDate, duration } keys.

So the root cause looks like the server is typing iterations against a named input type (ProjectV2IterationFieldConfigurationIterationInput) that doesn't exist in the public schema. Passing the list as an unnamed [JSON!]! / inline-object list (as the working mutation above does) should fix both tools.

Suggested fix

1. In create_iteration_field and add_iteration, stop referencing ProjectV2IterationFieldConfigurationIterationInput in the GraphQL variable declarations — inline the iterations list or type it as [ProjectV2IterationFieldConfigurationIterationInput!]! only if/when GitHub exposes it.
2. add_iteration additionally references startDate on the output type ProjectV2IterationFieldConfiguration, which doesn't exist there — that field lives on the individual iterations nodes. Adjust the selection set accordingly.
3. On create_iteration_field failure, consider rolling back the partially-created field so retries with the same name don't 409.

Environment

• Tool version: whatever is currently deployed on the MCP server as of 2026-04-13
• Client: Claude Code via MCP
• Target: public github.com GraphQL API

Happy to PR if helpful.