fix(mcp): stop DEFAULT_INSTRUCTIONS advertising a universal dry_run

.changeset/server-instructions-dry-run.md

@@ -0,0 +1,15 @@
+---
+"@contentrain/mcp": patch
+---
+
+fix(mcp): stop DEFAULT_INSTRUCTIONS advertising a universal dry_run
+
+The MCP server instructions told every client to "preview writes with
+dry_run:true, then re-run with dry_run:false" — but `dry_run` exists only on
+`contentrain_apply`. On every other write tool the unknown key is stripped by
+the schema, so an agent following the instructions performed a real write
+while believing it had previewed. The instructions now state the actual
+safety model: writes land on isolated `cr/*` branches, `content_save`
+validates before committing, destructive tools require `confirm:true`, and
+`dry_run` is the `contentrain_apply` preview. Still under the 512-character
+client-UI budget; no tool behavior changes.

packages/mcp/src/server.ts

@@ -29,12 +29,12 @@ import packageJson from '../package.json' with { type: 'json' }
  */
 export const DEFAULT_INSTRUCTIONS
   = 'Contentrain is git-native content governance: models define structure; '
-    + 'content is canonical JSON/Markdown on a dedicated branch. Call '
-    + 'contentrain_describe_format before creating models or content. Preview '
-    + 'writes with dry_run:true, review the plan, then re-run with '
-    + 'dry_run:false. Start with contentrain_status for models, locales, and '
-    + 'workflow; inspect a model with contentrain_describe before editing its '
-    + 'entries. Tools are deterministic infrastructure — content decisions '
+    + 'content is canonical JSON/Markdown on a dedicated branch. Start with '
+    + 'contentrain_status; call contentrain_describe_format before creating '
+    + 'models or content, and contentrain_describe before editing a model\'s '
+    + 'entries. Every write lands on an isolated cr/* branch and content_save '
+    + 'validates before committing. Destructive tools require confirm:true; '
+    + 'preview contentrain_apply with dry_run:true first. Content decisions '
     + 'stay with the agent.'
 
 export interface CreateServerOptions {