feat(bf-pxdn0): add SSRF_BLOCKED helper function signature

- Add standalone is_ssrf_blocked() function to mcp_helpers module
- Function accepts JsonRpcError reference and returns bool (stub returning false)
- Added comprehensive documentation with usage examples
- Located in TH-05-ssrf-block.rs after is_ssrf_blocked_error() function
- Verification: notes/bf-pxdn0.md

Closes bf-pxdn0

crates/pdftract-core/tests/TH-05-ssrf-block.rs

@@ -751,6 +751,42 @@ pub mod mcp_helpers {
         Ok(false)
     }
 
+    /// Check if a JsonRpcError indicates an SSRF_BLOCKED error.
+    ///
+    /// This is a standalone helper function that accepts a JsonRpcError reference
+    /// and returns a boolean indicating whether the error represents an SSRF_BLOCKED
+    /// condition.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - Reference to the JsonRpcError to check
+    ///
+    /// # Returns
+    ///
+    /// * `true` if the error indicates SSRF_BLOCKED
+    /// * `false` otherwise (currently a stub implementation)
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use mcp_helpers::{is_ssrf_blocked, JsonRpcError};
+    ///
+    /// let error = JsonRpcError {
+    ///     code: -32001,
+    ///     message: "SSRF_BLOCKED: URL rejected".to_string(),
+    ///     data: None,
+    /// };
+    ///
+    /// if is_ssrf_blocked(&error) {
+    ///     // Handle SSRF blocked error
+    /// }
+    /// ```
+    pub fn is_ssrf_blocked(error: &JsonRpcError) -> bool {
+        // Stub implementation - returns false for now
+        // TODO: Implement proper SSRF_BLOCKED detection logic
+        false
+    }
+
     /// Extract error information from a JSON-RPC error response.
     ///
     /// Returns a tuple of (code, message, optional_data) for easier error handling.

notes/bf-pxdn0.md

@@ -0,0 +1,46 @@
+# Bead bf-pxdn0: Add SSRF_BLOCKED helper function signature
+
+## Summary
+
+Added a standalone helper function `is_ssrf_blocked()` to the `mcp_helpers` module in the TH-05 SSRF test file. The function accepts a `JsonRpcError` reference and returns a boolean.
+
+## Implementation
+
+**File Modified:** `/home/coding/pdftract/crates/pdftract-core/tests/TH-05-ssrf-block.rs`
+
+**Function Added:**
+```rust
+pub fn is_ssrf_blocked(error: &JsonRpcError) -> bool {
+    // Stub implementation - returns false for now
+    // TODO: Implement proper SSRF_BLOCKED detection logic
+    false
+}
+```
+
+**Location:** Added after the `is_ssrf_blocked_error()` function (around line 754) in the `mcp_helpers` module.
+
+## Acceptance Criteria Status
+
+- ✅ **PASS**: Function exists with correct signature accepting `JsonRpcError` reference
+- ✅ **PASS**: Function returns `bool` type
+- ✅ **PASS**: Function compiles successfully (verified with `cargo check --tests -p pdftract-core`)
+- ✅ **PASS**: Function is a stub that returns `false`
+
+## Notes
+
+- The function is added as a standalone helper in the `mcp_helpers` module (line 754-770)
+- It follows the same pattern as other helper functions in the module (e.g., `is_ssrf_blocked_error()`)
+- The function is well-documented with comprehensive doc comments including usage examples
+- This provides a clean API for checking SSRF errors separate from the method on `JsonRpcError` itself
+- The implementation is intentionally left as a stub (returns `false`) as specified in the acceptance criteria
+
+## Testing
+
+The code compiles successfully without any errors. The function signature matches the requirements exactly and can be called with a `JsonRpcError` reference:
+
+```rust
+let error = JsonRpcError { /* ... */ };
+if is_ssrf_blocked(&error) {
+    // Handle SSRF blocked case
+}
+```