diff --git a/CLAUDE.md b/CLAUDE.md
index 301485c..e59b61d 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -50,6 +50,18 @@ To add a new source: create `sources/<name>/` with a `tools.py` that exposes
 `register(mcp, ...)`, then call it from `server.build_server`. Keep tool
 names prefixed with the source so they don't collide.
 
+The server is launched via `uv run` (see `.mcp.json`), so `uv` must be on the
+user's PATH. A `SessionStart` hook (`hooks/hooks.json`) checks for uv at
+session start and, when missing, prints install instructions to the user (and
+tells Claude the tools are unavailable) instead of letting the server fail
+silently. It ships in two shell-pinned flavours so it runs whichever shell
+Claude Code picks: `hooks/check-uv.sh` (bash; macOS/Linux/Windows+Git Bash)
+and `hooks/check-uv.ps1` (PowerShell; Windows without Git Bash) — both emit
+the same SessionStart JSON. Neither depends on uv itself, and both stay silent
+on the happy path. The `.ps1` path has not been exercised on a real Windows
+host yet (cross-platform `shell`-field behaviour is undocumented), so verify
+there before relying on it.
+
 ## Instructions
 
 * To determine if a change was successful, run the test suite.
diff --git a/README.md b/README.md
index 0bff534..7a14a43 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,28 @@ This repository ships as a Claude Code plugin (the `.claude-plugin/`
 directory and the `research-person` skill under `skills/`). You can also
 run the MCP server stand-alone against any MCP client.
 
+## Requirements
+
+[**uv**](https://docs.astral.sh/uv/) must be installed and on your `PATH` —
+the MCP server is launched with `uv run` (see `.mcp.json`), which also
+installs the Python dependencies on first run. Without uv the server cannot
+start and none of the tools load. Install it with:
+
+```bash
+# macOS / Linux
+curl -LsSf https://astral.sh/uv/install.sh | sh
+
+# Windows (PowerShell)
+irm https://astral.sh/uv/install.ps1 | iex
+```
+
+then restart Claude Code. As a convenience the plugin runs a `SessionStart`
+hook that detects a missing uv and prints these instructions instead of
+failing silently. The check ships in two flavours so it works regardless of
+the shell Claude Code uses: `hooks/check-uv.sh` (bash — macOS, Linux, and
+Windows with Git Bash) and `hooks/check-uv.ps1` (PowerShell — Windows
+without Git Bash); `hooks/hooks.json` pins each to its shell.
+
 ## Configuration
 
 Every knob can be set three ways. Precedence, highest to lowest:
diff --git a/hooks/check-uv.ps1 b/hooks/check-uv.ps1
new file mode 100644
index 0000000..9bacc2b
--- /dev/null
+++ b/hooks/check-uv.ps1
@@ -0,0 +1,40 @@
+# SessionStart hook (PowerShell variant) for the genealogy plugin.
+#
+# Mirrors check-uv.sh for Windows hosts where Claude Code runs hooks via
+# PowerShell (i.e. Git Bash is not installed). The genealogy MCP server is
+# launched with `uv run`; if `uv` is missing the server never starts and its
+# tools silently fail to load. This warns the user instead.
+#
+# Stays silent (exit 0, no output) on the happy path.
+$ErrorActionPreference = 'Stop'
+
+if (Get-Command uv -ErrorAction SilentlyContinue) {
+    exit 0
+}
+
+# uv not found. Emit the same SessionStart JSON shape as check-uv.sh:
+#   systemMessage                        -> shown to the user
+#   hookSpecificOutput.additionalContext -> injected into Claude's context
+# ConvertTo-Json handles all escaping (newlines, non-ASCII) for us.
+$userMsg = @"
+⚠️  genealogy plugin: 'uv' was not found on your PATH.
+
+The genealogy MCP server is launched with 'uv run', so its tools (heredis_*, geneteka_*, basia_*, …) will not load until uv is installed.
+
+Install uv → https://docs.astral.sh/uv/getting-started/installation/
+    irm https://astral.sh/uv/install.ps1 | iex
+Then restart Claude Code.
+"@
+
+$ctx = "The 'uv' CLI is not installed on this machine. The genealogy MCP server runs via 'uv run', so all genealogy plugin tools (heredis_*, gedcom_*, geneteka_*, genbaza_*, lubgens_*, basia_*, genpod_*, genealogyindexer_*, familysearch_*) are unavailable until the user installs uv (https://docs.astral.sh/uv) and restarts Claude Code. If asked to use any of these tools, explain this rather than attempting to call them."
+
+$payload = [ordered]@{
+    systemMessage      = $userMsg
+    hookSpecificOutput = [ordered]@{
+        hookEventName     = 'SessionStart'
+        additionalContext = $ctx
+    }
+}
+
+$payload | ConvertTo-Json -Compress -Depth 5
+exit 0
diff --git a/hooks/check-uv.sh b/hooks/check-uv.sh
new file mode 100755
index 0000000..0f7c5cd
--- /dev/null
+++ b/hooks/check-uv.sh
@@ -0,0 +1,27 @@
+#!/usr/bin/env sh
+# SessionStart hook for the genealogy plugin.
+#
+# The genealogy MCP server is launched via `uv run` (see .mcp.json). If `uv`
+# is not on the user's PATH the server never starts and its tools silently
+# fail to load — a confusing failure mode. This hook checks for uv at session
+# start and, when it is missing, surfaces a clear, actionable message to the
+# user and tells Claude the tools are unavailable.
+#
+# Stays silent (exit 0, no output) on the happy path so it never adds noise.
+set -eu
+
+if command -v uv >/dev/null 2>&1; then
+  exit 0
+fi
+
+# uv not found. Emit SessionStart JSON:
+#   systemMessage                       -> shown to the user
+#   hookSpecificOutput.additionalContext -> injected into Claude's context
+# Newlines are written as literal \n (valid JSON escapes); printf's %s passes
+# the backslash-n through untouched.
+user_msg="⚠️  genealogy plugin: 'uv' was not found on your PATH.\n\nThe genealogy MCP server is launched with 'uv run', so its tools (heredis_*, geneteka_*, basia_*, …) will not load until uv is installed.\n\nInstall uv → https://docs.astral.sh/uv/getting-started/installation/\n    curl -LsSf https://astral.sh/uv/install.sh | sh\nThen restart Claude Code."
+
+ctx="The 'uv' CLI is not installed on this machine. The genealogy MCP server runs via 'uv run', so all genealogy plugin tools (heredis_*, gedcom_*, geneteka_*, genbaza_*, lubgens_*, basia_*, genpod_*, genealogyindexer_*, familysearch_*) are unavailable until the user installs uv (https://docs.astral.sh/uv) and restarts Claude Code. If asked to use any of these tools, explain this rather than attempting to call them."
+
+printf '{"systemMessage":"%s","hookSpecificOutput":{"hookEventName":"SessionStart","additionalContext":"%s"}}\n' "$user_msg" "$ctx"
+exit 0
diff --git a/hooks/hooks.json b/hooks/hooks.json
new file mode 100644
index 0000000..ae8cdef
--- /dev/null
+++ b/hooks/hooks.json
@@ -0,0 +1,36 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "matcher": "startup",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "\"${CLAUDE_PLUGIN_ROOT}/hooks/check-uv.sh\"",
+            "shell": "bash"
+          },
+          {
+            "type": "command",
+            "command": "Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass -Force; & \"${CLAUDE_PLUGIN_ROOT}/hooks/check-uv.ps1\"",
+            "shell": "powershell"
+          }
+        ]
+      },
+      {
+        "matcher": "resume",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "\"${CLAUDE_PLUGIN_ROOT}/hooks/check-uv.sh\"",
+            "shell": "bash"
+          },
+          {
+            "type": "command",
+            "command": "Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass -Force; & \"${CLAUDE_PLUGIN_ROOT}/hooks/check-uv.ps1\"",
+            "shell": "powershell"
+          }
+        ]
+      }
+    ]
+  }
+}