Client survey
What MCP clients forward to the model
How MCP clients convert a CallToolResult before
forwarding it to the model — and why most forward only
content.
Structured content in MCP tool results
Two paired surveys of content vs
structuredContent in MCP tool results. The client survey
explains what reaches the model; the server survey explains what servers
put on the wire — the same degenerate equilibrium from opposite ends.
Write-ups
Server survey
What servers actually put on the wire
What 22 popular MCP servers actually emit — overwhelmingly content-only, with only a few dual-writing, and those mainly to drive UI rendering.
The two surveys are companions and cross-link to each other. Source and the Markdown renderings live on GitHub.