diff --git a/rust/crates/sift_mcp/CLAUDE.md b/rust/crates/sift_mcp/CLAUDE.md
index f8a368b7f6..6644dee492 100644
--- a/rust/crates/sift_mcp/CLAUDE.md
+++ b/rust/crates/sift_mcp/CLAUDE.md
@@ -492,7 +492,7 @@ When you add or update a list tool:
    your own words risks drift; quoting from the proto keeps the tool aligned with the API.
 3. **Map every wrapped field to a bullet** under `Parameters:`, following Step 4's structure:
    - Filter: list every filterable field named in the proto's `filter` comment. Preserve
-     metadata-key syntax (`metadata.{key}`) and CEL helpers (`duration(...)`).
+     metadata-key syntax (`metadata["<key>"]`) and CEL helpers (`duration(...)`).
    - Order-by: list every orderable field, the default sort when the field is empty (assets and
      runs default to `created_date desc`; channels defaults to `created_date` ascending — these
      differ, do not assume), and the `\"FIELD_NAME[ desc],...\"` format.
diff --git a/rust/crates/sift_mcp/src/server/test.rs b/rust/crates/sift_mcp/src/server/test.rs
index 8ae0230193..0124f90a3d 100644
--- a/rust/crates/sift_mcp/src/server/test.rs
+++ b/rust/crates/sift_mcp/src/server/test.rs
@@ -193,6 +193,58 @@ async fn feature_flag_gates_test_report_tools() {
     enabled_handle.abort();
 }
 
+/// The `filter` parameter bullet of a tool description, up to the next bullet or blank line.
+fn filter_bullet(description: &str) -> String {
+    let mut lines = description
+        .lines()
+        .skip_while(|line| !line.trim_start().starts_with("- `filter`:"));
+    let Some(first) = lines.next() else {
+        return String::new();
+    };
+    let rest = lines.take_while(|line| {
+        let line = line.trim_start();
+        !line.is_empty() && !line.starts_with("- ")
+    });
+    std::iter::once(first)
+        .chain(rest)
+        .collect::<Vec<_>>()
+        .join("\n")
+}
+
+/// The filter service only declares metadata keys as `metadata["<key>"]` and rejects
+/// `metadata.<key>`. An agent that copies a dot-form example concludes metadata can't
+/// be filtered, so every `filter` that takes metadata must show the bracket form and no
+/// description may show a dot-form key.
+#[tokio::test]
+async fn tool_descriptions_use_bracket_metadata_syntax() {
+    let (server, handle) =
+        server_with_feature_flags(None, 0, ClientEventReporter::default(), all_feature_flags())
+            .await;
+    let mut metadata_filters = 0;
+    for tool in server.tool_router.list_all() {
+        let description = tool.description.as_deref().unwrap_or_default();
+        let filter = filter_bullet(description);
+        if filter.contains("metadata") {
+            metadata_filters += 1;
+            assert!(
+                filter.contains(r#"`metadata["<key>"]`"#),
+                "{} filters on metadata without showing the bracket syntax",
+                tool.name
+            );
+        }
+        for (i, _) in description.match_indices("metadata.") {
+            let next = description[i + "metadata.".len()..].chars().next();
+            assert!(
+                !next.is_some_and(|c| c == '{' || c == '_' || c.is_ascii_alphanumeric()),
+                "{} shows the unsupported dot metadata syntax",
+                tool.name
+            );
+        }
+    }
+    assert!(metadata_filters > 0, "no `filter` bullet mentions metadata");
+    handle.abort();
+}
+
 #[tokio::test]
 async fn each_feature_flag_gates_only_its_own_tools() {
     for &(_, flag) in TOOL_FEATURE_FLAGS {
diff --git a/rust/crates/sift_mcp/src/tool/annotations/mod.rs b/rust/crates/sift_mcp/src/tool/annotations/mod.rs
index 7196565706..2f3bc4007d 100644
--- a/rust/crates/sift_mcp/src/tool/annotations/mod.rs
+++ b/rust/crates/sift_mcp/src/tool/annotations/mod.rs
@@ -143,7 +143,7 @@ impl SiftMcpServer {
                 `description`, `state`, `created_by_user_id`, `created_by_rule_condition_version_id`, `rule_id`,
                 `annotation_type`, `tag_name`, `report_id`, `asset_id`, `asset_name`, `pending`, `assignee`,
                 `campaign_reports`, `metadata`, `archived_date`, `is_archived`. Reference metadata entries as
-                `metadata.{key}` (e.g. `metadata.severity == \"high\"`).
+                `metadata[\"<key>\"]` (e.g. `metadata[\"severity\"] == \"high\"`).
                 Compare `state` with `ANNOTATION_STATE_OPEN`, `ANNOTATION_STATE_FLAGGED`, or
                 `ANNOTATION_STATE_RESOLVED`. Compare `annotation_type` with `ANNOTATION_TYPE_DATA_REVIEW` or
                 `ANNOTATION_TYPE_PHASE`. Use these exact string enum values in quoted filter operands.
diff --git a/rust/crates/sift_mcp/src/tool/assets/mod.rs b/rust/crates/sift_mcp/src/tool/assets/mod.rs
index 9095cb820a..b3e9babe71 100644
--- a/rust/crates/sift_mcp/src/tool/assets/mod.rs
+++ b/rust/crates/sift_mcp/src/tool/assets/mod.rs
@@ -47,7 +47,7 @@ impl SiftMcpServer {
               - `filter`: CEL expression. Pass an empty string to list everything. Filterable fields:
                 `asset_id`, `name`, `name_lower`, `tag_id`, `tag_name`, `created_date`, `modified_date`,
                 `archived_date`, `is_archived`, `created_by_user_id`, `modified_by_user_id`, `metadata`.
-                Reference metadata entries as `metadata.{key}` (e.g. `metadata.vehicle_type == \"rover\"`).
+                Reference metadata entries as `metadata[\"<key>\"]` (e.g. `metadata[\"vehicle_type\"] == \"rover\"`).
                 When searching by name, use `name_lower.contains(\"rover\")`: `name_lower` is an indexed lowercase
                 copy of `name` and exists only on assets. On any other text field use `name.matches(\"(?i)rover\")`.
                 Use `==` only for an exact value from a prior result. `contains`/`startsWith`/`endsWith` are
diff --git a/rust/crates/sift_mcp/src/tool/report_templates/mod.rs b/rust/crates/sift_mcp/src/tool/report_templates/mod.rs
index 3eacf0f958..863bb294f2 100644
--- a/rust/crates/sift_mcp/src/tool/report_templates/mod.rs
+++ b/rust/crates/sift_mcp/src/tool/report_templates/mod.rs
@@ -70,7 +70,7 @@ impl SiftMcpServer {
             Parameters:
               - `filter`: CEL expression. Pass an empty string to list everything. Filterable fields:
                 `report_template_id`, `tag_id`, `tag_name`, `client_key`, `metadata`, `name`, `is_archived`.
-                Reference metadata entries as `metadata.{key}` (e.g. `metadata.owner == \"qa-team\"`).
+                Reference metadata entries as `metadata[\"<key>\"]` (e.g. `metadata[\"owner\"] == \"qa-team\"`).
                 When filtering or searching, use `name.matches(\"(?i)avionics\")`, not `==`. Use `==` only for an
                 exact value from a prior result. `contains`/`startsWith`/`endsWith` are case-SENSITIVE:
                 `contains(\"Avionics\")` silently misses `avionics-power-limit`.
diff --git a/rust/crates/sift_mcp/src/tool/reports/mod.rs b/rust/crates/sift_mcp/src/tool/reports/mod.rs
index 6569adf00c..4b73e3bc3e 100644
--- a/rust/crates/sift_mcp/src/tool/reports/mod.rs
+++ b/rust/crates/sift_mcp/src/tool/reports/mod.rs
@@ -73,7 +73,7 @@ impl SiftMcpServer {
                 `report_id`, `report_template_id`, `tag_name`, `name`, `run_id`, `report_type`, `is_archived`,
                 `archived_date`, `created_date`, `created_by_user_id`, `metadata`, `modified_date`,
                 `modified_by_user_id`.
-                Reference metadata entries as `metadata.{key}` (e.g. `metadata.batch == \"nightly\"`).
+                Reference metadata entries as `metadata[\"<key>\"]` (e.g. `metadata[\"batch\"] == \"nightly\"`).
                 When filtering or searching, use `name.matches(\"(?i)nightly\")`, not `==`. Use `==` only for an
                 exact value from a prior result. `contains`/`startsWith`/`endsWith` are case-SENSITIVE:
                 `contains(\"Nightly\")` silently misses `nightly-regression`.
diff --git a/rust/crates/sift_mcp/src/tool/rules/mod.rs b/rust/crates/sift_mcp/src/tool/rules/mod.rs
index eddbfa2ac6..a82f632490 100644
--- a/rust/crates/sift_mcp/src/tool/rules/mod.rs
+++ b/rust/crates/sift_mcp/src/tool/rules/mod.rs
@@ -78,7 +78,7 @@ impl SiftMcpServer {
                 `rule_id`, `client_key`, `name`, `description`, `is_external`, `asset_id`, `tag_id`,
                 `created_date`, `created_by_user_id`, `metadata`, `modified_date`, `modified_by_user_id`,
                 `deleted_date`, `is_archived`, `archived_date`, `is_live_evaluation_enabled`.
-                Reference metadata entries as `metadata.{key}` (e.g. `metadata.severity == \"high\"`).
+                Reference metadata entries as `metadata[\"<key>\"]` (e.g. `metadata[\"severity\"] == \"high\"`).
                 When filtering or searching, use `name.matches(\"(?i)avionics\")`, not `==`. Use `==` only for an
                 exact value from a prior result. `contains`/`startsWith`/`endsWith` are case-SENSITIVE:
                 `contains(\"Avionics\")` silently misses `avionics-power-limit`.
diff --git a/rust/crates/sift_mcp/src/tool/runs/mod.rs b/rust/crates/sift_mcp/src/tool/runs/mod.rs
index b1f230ecfc..6f19244460 100644
--- a/rust/crates/sift_mcp/src/tool/runs/mod.rs
+++ b/rust/crates/sift_mcp/src/tool/runs/mod.rs
@@ -56,7 +56,7 @@ impl SiftMcpServer {
                 `start_time`, `stop_time`, `duration`, `duration_string`, `tag_id`, `asset_tag_id`,
                 `annotation_comments_count`, `annotation_state`, `created_date`, `modified_date`, `archived_date`,
                 `is_archived`, `created_by_user_id`, `modified_by_user_id`, `metadata`.
-                Reference metadata entries as `metadata.{key}`.
+                Reference metadata entries as `metadata[\"<key>\"]`.
                 `duration` is elapsed seconds (numeric). `duration_string` accepts `h`/`m`/`s`/`ms` suffixes via the
                 `duration(...)` helper, e.g. `duration_string > duration('10h')`.
                 When filtering or searching, use `name.matches(\"(?i)rover\")`, not `==`. Use `==` only for an
diff --git a/rust/crates/sift_mcp/src/tool/test_reports/mod.rs b/rust/crates/sift_mcp/src/tool/test_reports/mod.rs
index b64898f77e..1ecbd354c1 100644
--- a/rust/crates/sift_mcp/src/tool/test_reports/mod.rs
+++ b/rust/crates/sift_mcp/src/tool/test_reports/mod.rs
@@ -68,7 +68,7 @@ impl SiftMcpServer {
                 `test_report_id`, `status`, `name`, `test_system_name`, `test_case`, `start_time`, `end_time`,
                 `serial_number`, `part_number`, `system_operator`, `run_id`, `archived_date`,
                 `created_by_user_id`, `modified_by_user_id`, `metadata`. Reference metadata entries as
-                `metadata.{key}`. `status` matches the `TestStatus` enum: `TEST_STATUS_DRAFT`,
+                `metadata[\"<key>\"]`. `status` matches the `TestStatus` enum: `TEST_STATUS_DRAFT`,
                 `TEST_STATUS_PASSED`, `TEST_STATUS_FAILED`, `TEST_STATUS_ABORTED`, `TEST_STATUS_ERROR`,
                 `TEST_STATUS_IN_PROGRESS`, `TEST_STATUS_SKIPPED`. Filtering `test_report_id == \"...\"` fetches one
                 report (there is no separate get tool).
@@ -150,9 +150,10 @@ impl SiftMcpServer {
               - `filter`: CEL expression. Pass an empty string to list everything (rarely useful; almost always
                 scope by `test_report_id`). Filterable fields: `test_step_id`, `test_report_id`, `parent_step_id`,
                 `name`, `description`, `step_type`, `step_path`, `status`, `start_time`, `end_time`, `error_code`,
-                `error_message`, `created_date`, `modified_date`, `metadata`. `step_type` matches the
-                `TestStepType` enum: `TEST_STEP_TYPE_SEQUENCE`, `TEST_STEP_TYPE_GROUP`, `TEST_STEP_TYPE_ACTION`,
-                `TEST_STEP_TYPE_FLOW_CONTROL`. `status` matches `TestStatus` (see `list_test_reports`).
+                `error_message`, `created_date`, `modified_date`, `metadata`. Reference metadata entries as
+                `metadata[\"<key>\"]`. `step_type` matches the `TestStepType` enum: `TEST_STEP_TYPE_SEQUENCE`,
+                `TEST_STEP_TYPE_GROUP`, `TEST_STEP_TYPE_ACTION`, `TEST_STEP_TYPE_FLOW_CONTROL`. `status` matches
+                `TestStatus` (see `list_test_reports`).
                 When filtering or searching `name`, `description`, or `error_message`, use
                 `name.matches(\"(?i)power\")`, not `==`. Use `==` only for an exact value from a prior result.
                 `contains`/`startsWith`/`endsWith` are case-SENSITIVE: `contains(\"Power\")` silently misses
@@ -232,9 +233,10 @@ impl SiftMcpServer {
               - `filter`: CEL expression. Pass an empty string to list everything (almost always scope by
                 `test_report_id` or `test_step_id`). Filterable fields: `measurement_id`, `measurement_type`,
                 `name`, `test_step_id`, `test_report_id`, `numeric_value`, `string_value`, `boolean_value`,
-                `passed`, `timestamp`, `created_date`, `modified_date`, `metadata`. `measurement_type` matches the
-                `TestMeasurementType` enum: `TEST_MEASUREMENT_TYPE_DOUBLE`, `TEST_MEASUREMENT_TYPE_STRING`,
-                `TEST_MEASUREMENT_TYPE_BOOLEAN`, `TEST_MEASUREMENT_TYPE_LIMIT`.
+                `passed`, `timestamp`, `created_date`, `modified_date`, `metadata`. Reference metadata entries as
+                `metadata[\"<key>\"]`. `measurement_type` matches the `TestMeasurementType` enum:
+                `TEST_MEASUREMENT_TYPE_DOUBLE`, `TEST_MEASUREMENT_TYPE_STRING`, `TEST_MEASUREMENT_TYPE_BOOLEAN`,
+                `TEST_MEASUREMENT_TYPE_LIMIT`.
                 When filtering or searching `name`, use `name.matches(\"(?i)voltage\")`, not `==`. Use `==` only
                 for an exact value from a prior result. `contains`/`startsWith`/`endsWith` are case-SENSITIVE:
                 `contains(\"Voltage\")` silently misses `voltage_bus_a`.
@@ -302,10 +304,10 @@ impl SiftMcpServer {
               - `filter`: CEL expression. Pass an empty string to count all steps. Filterable fields are identical
                 to `list_test_steps`: `test_step_id`, `test_report_id`, `parent_step_id`, `name`, `description`,
                 `step_type`, `step_path`, `status`, `start_time`, `end_time`, `error_code`, `error_message`,
-                `created_date`, `modified_date`, `metadata`. When filtering `name`, `description`, or
-                `error_message`, use `name.matches(\"(?i)power\")`, not `==`. Use `==` only for an exact value from
-                a prior result. `contains`/`startsWith`/`endsWith` are case-SENSITIVE: `contains(\"Power\")`
-                silently misses `power-on`.
+                `created_date`, `modified_date`, `metadata`. Reference metadata entries as `metadata[\"<key>\"]`.
+                When filtering `name`, `description`, or `error_message`, use `name.matches(\"(?i)power\")`, not
+                `==`. Use `==` only for an exact value from a prior result. `contains`/`startsWith`/`endsWith` are
+                case-SENSITIVE: `contains(\"Power\")` silently misses `power-on`.
 
             Errors:
               - `INVALID_PARAMS` if `filter` is not a valid CEL expression.
@@ -340,10 +342,10 @@ impl SiftMcpServer {
               - `filter`: CEL expression. Pass an empty string to count all measurements. Filterable fields are
                 identical to `list_test_measurements`: `measurement_id`, `measurement_type`, `name`,
                 `test_step_id`, `test_report_id`, `numeric_value`, `string_value`, `boolean_value`, `passed`,
-                `timestamp`, `created_date`, `modified_date`, `metadata`. When filtering `name`, use
-                `name.matches(\"(?i)voltage\")`, not `==`. Use `==` only for an exact value from a prior result.
-                `contains`/`startsWith`/`endsWith` are case-SENSITIVE: `contains(\"Voltage\")` silently misses
-                `voltage_bus_a`.
+                `timestamp`, `created_date`, `modified_date`, `metadata`. Reference metadata entries as
+                `metadata[\"<key>\"]`. When filtering `name`, use `name.matches(\"(?i)voltage\")`, not `==`. Use
+                `==` only for an exact value from a prior result. `contains`/`startsWith`/`endsWith` are
+                case-SENSITIVE: `contains(\"Voltage\")` silently misses `voltage_bus_a`.
 
             Errors:
               - `INVALID_PARAMS` if `filter` is not a valid CEL expression.