MCP Server Gaps Blocking End-to-End Agent Content Workflows

[marcusbellamyshaw-cell]

MCP Server Gaps Blocking End-to-End Agent Content Workflows

Context

I’m running an Emdash-powered content site (everybittexas.com) and managing it primarily through Claude’s MCP connector on mobile (iPhone app). The goal is a fully agent-driven publishing workflow: write article → create tags → upload media → assign taxonomies → set SEO metadata → save as draft.

The MCP server handles article creation, tag creation, and content updates well. But three operations that exist in the REST API are either missing or broken in the MCP surface, which forces manual admin UI work for every post.

Gap 1: No content_set_terms MCP Tool

REST API has it:

POST /_emdash/api/content/:collection/:id/terms/:taxonomy
{ "termIds": ["term_abc", "term_def"] }

MCP does not. The MCP server exposes taxonomy CRUD tools (taxonomy_create_term, taxonomy_list_terms, etc.) but has no tool to assign terms to content items. This means an agent can create a post and create the tags, but cannot wire them together.

Impact: Every post requires a manual trip to the admin UI to assign categories, tags, regions, and eras — even though the agent already knows exactly which term IDs to assign.

Suggested fix: Add a content_set_terms MCP tool that mirrors the REST endpoint. Something like:

content_set_terms({
  collection: "posts",
  id: "01ABC123",
  taxonomy: "category",
  termIds: ["01KREG5KXBDC0BEW3TH918H4J8"]
})

Gap 2: content_update SEO Parameter Serialization Failure

The content_update MCP tool schema includes an seo parameter with a ContentSeoInput type:

"seo": {
  "allOf": [{ "$ref": "#/definitions/ContentSeoInput" }],
  "description": "Per-content SEO metadata..."
}

When called from Claude’s MCP client with a valid object:

{
  "collection": "posts",
  "id": "01KRSAHVZVJ1TQ7H2ESCSYS50M",
  "seo": {
    "title": "Cowboy Mardi Gras in Bandera, Texas",
    "description": "Bandera's Cowboy Mardi Gras blends Cajun flavor with Hill Country grit..."
  }
}

It returns:

[VALIDATION_ERROR] Invalid arguments for tool content_update:
[{ "expected": "object", "code": "invalid_type", "path": ["seo"], "message": "Invalid input" }]

The data parameter (typed as plain "type": "object") works fine in the same call. The issue appears to be with how the allOf + $ref schema pattern is handled — either by the MCP server’s input validator not resolving the $ref before type-checking, or by the client’s serialization layer passing the value as a string instead of an object. Hard to tell from the error alone which side is dropping it.

Impact: SEO title and meta description must be set manually in the admin for every post.

Suggested fix: Either inline the ContentSeoInput schema instead of using allOf/$ref, or ensure the MCP input validator resolves $ref definitions before validation. This may also affect the bylines parameter which uses a similar pattern.

Gap 3: Media Upload Path for MCP Agents

This one is documented and intentional — MCP transport can’t carry binary uploads, and the media_create tool registers metadata for files already in storage. The signed-upload flow requires direct HTTP access to the Emdash instance, which MCP clients like Claude.ai don’t have (Claude’s container can’t reach arbitrary domains).

I have paid Cloudflare Workers, so one possible workaround would be a plugin that accepts a media URL and handles the upload server-side. But a native solution would be cleaner.

Possible approaches:

• An MCP tool like media_upload_from_url that fetches a remote image URL server-side and registers it in the media library
• A tool that returns a signed upload URL the MCP client could use (though this still has the outbound network limitation for some clients)

Environment

• Emdash version: 0.12.0 (29eeee7)
• MCP client: Claude.ai mobile app (iPhone), MCP connector
• Deployment: Cloudflare Workers (paid account with Dynamic Workers)
• Auth: Personal Access Token with Content Read/Write, Media Read/Write, Schema Read/Write, Taxonomies Manage scopes

Summary

Operation	REST API	MCP	Status
Create content	✅	✅	Works
Update content fields	✅	✅	Works
Create taxonomy terms	✅	✅	Works
Assign terms to content	✅	❌	Tool missing
Set per-content SEO	✅	⚠️	Validation bug
Upload media	✅	❌	Transport limitation

Gaps 1 and 2 seem like straightforward additions/fixes. Gap 3 is a harder transport-level problem, but media_upload_from_url would cover the most common agent use case (working from Library of Congress images, stock photo URLs, etc.).

Happy to help test any of these if there’s a branch to try.

[marcusbellamyshaw-cell]

Built a plugin that works around gaps 1 and 2 while waiting on native MCP support: https://github.com/marcusbellamyshaw-cell/emdash-auto-meta — happy to collaborate if any of this is useful upstream.