# X_MCP_EFFECT_CONFLICT

## Means

a read-only MCP tool declares an effect

## Typical cause

a query (or a tool declared destructive: false) carries mcp.effect, and on a meta-split surface a read is always read_resource's

## Fix

`drop effect from the query's mcp block, or make it an action if it writes`

[MCP and AI](/error-codes#mcp-and-ai)