`update_pull_request_reviewers` should accept email addresses, not just identity GUIDs

[kimsey0]

Summary

Adding a reviewer to a pull request currently requires a 3-step chain:

1. repo_get_repo_by_name_or_id -- resolve repository name to GUID (unless already known)
2. core_get_identity_ids -- resolve email address (e.g. bfs@templafy.com) to identity GUID (e.g. 3e13f7bd-d0b0-6ed9-a45d-b4e22eb7dc22)
3. repo_update_pull_request_reviewers -- actually add the reviewer using the GUID

Step 2 exists solely because reviewerIds only accepts identity GUIDs. The server already has the core_get_identity_ids tool and thus the capability to resolve identities -- it just doesn't do it inline.

Example of the current workflow

// Step 1: Look up identity GUID
// Tool: core_get_identity_ids
{ "searchFilter": "jdoe@example.com" }
// Result: [{ "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890", "displayName": "Jane Doe" }]

// Step 2: Add reviewer using GUID
// Tool: repo_update_pull_request_reviewers
{
  "repositoryId": "MyRepositoryName",
  "project": "MyProjectName",
  "pullRequestId": 12345,
  "reviewerIds": ["a1b2c3d4-e5f6-7890-abcd-ef1234567890"],
  "action": "add"
}

Suggested fix

Accept email addresses or display names in reviewerIds in addition to GUIDs, and resolve them server-side. The server can detect whether a value is a GUID (matches UUID format) or a search string, and call the identity resolution API internally for non-GUID values.

Alternatively, add a parallel parameter like reviewerEmails that resolves emails to IDs before calling the Azure DevOps API.

Why this matters

This is one of the most common PR workflows - adding a reviewer. The extra lookup step:

• Adds latency (an extra round-trip tool call)
• Consumes tokens (the identity resolution response is verbose)
• Is error-prone (the model must correctly thread the GUID from one response into the next request)

In my Claude Code sessions, this pattern appeared repeatedly across PR creation workflows.