web-debug-mcp

by MarlonJD

Overview Schema Source Related Servers Discussions Admin

TypeScript

Local

Control paused JavaScript debugger

web_debug_control

Destructive

Resume or step a paused local JavaScript target.

Instructions

Resume or step a paused local JavaScript target.

Input Schema

Name	Required	Description	Default
`action`	Yes
`sessionId`	Yes

Output Schema

Name	Required	Description	Default
`ok`	Yes
`data`	No
`error`	No
`warnings`	Yes
`artifacts`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed7 schema fields changedv0.12.0Oct 15, 2026

addedOutput schema / definitions / DebuggerSnapshotOutput / properties / breakpoints / items / properties / coordinateSpace
```
Added value: +{
+  "enum": [
+    "generated",
+    "original"
+  ],
+  "type": "string"
+}
```
addedOutput schema / definitions / DebuggerSnapshotOutput / properties / breakpoints / items / properties / resolved
```
Added value: +{
+  "allOf": [
+    {
+      "$ref": "#/definitions/SourceLocationOutput"
+    }
+  ]
+}
```
addedOutput schema / definitions / DebuggerSnapshotOutput / properties / breakpoints / items / properties / scriptId
```
Added value: +{
+  "maxLength": 100,
+  "type": "string"
+}
```
addedOutput schema / definitions / DebuggerSnapshotOutput / properties / breakpoints / items / properties / status
```
Added value: +{
+  "enum": [
+    "resolved",
+    "stale"
+  ],
+  "type": "string"
+}
```
addedOutput schema / definitions / DebuggerSnapshotOutput / properties / callFrames / items / properties / source
```
Added value: +{
+  "allOf": [
+    {
+      "$ref": "#/definitions/SourceReferenceOutput"
+    }
+  ]
+}
```

addedOutput schema / definitions / SourceLocationOutput

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "column": {
+      "exclusiveMinimum": 0,
+      "maximum": 9007199254740991,
+      "type": "integer"
+    },
+    "line": {
+      "exclusiveMinimum": 0,
+      "maximum": 9007199254740991,
+      "type": "integer"
+    },
+    "url": {
+      "maxLength": 2560,
+      "type": "string"
+    }
+  },
+  "required": [
+    "url",
+    "line",
+    "column"
+  ],
+  "type": "object"
+}

addedOutput schema / definitions / SourceReferenceOutput

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "generated": {
+      "$ref": "#/definitions/SourceLocationOutput"
+    },
+    "mapping": {
+      "enum": [
+        "mapped",
+        "unavailable"
+      ],
+      "type": "string"
+    },
+    "original": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/SourceLocationOutput"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "reason": {
+      "maxLength": 500,
+      "type": "string"
+    },
+    "scriptHash": {
+      "anyOf": [
+        {
+          "maxLength": 128,
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "scriptId": {
+      "maxLength": 100,
+      "type": "string"
+    }
+  },
+  "required": [
+    "scriptId",
+    "scriptHash",
+    "generated",
+    "original",
+    "mapping"
+  ],
+  "type": "object"
+}

Changed8 schema fields changedv0.10.0Sep 8, 2026

addedOutput schema / definitions / DebuggerSnapshotOutput

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "breakpoints": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "column": {
+            "anyOf": [
+              {
+                "maximum": 9007199254740991,
+                "minimum": -9007199254740991,
+                "type": "integer"
+              },
+              {
+                "type": "null"
+              }
+            ]
+          },
+          "id": {
+            "maxLength": 500,
+            "type": "string"
+          },
+          "line": {
+            "maximum": 9007199254740991,
+            "minimum": -9007199254740991,
+            "type": "integer"
+          },
+          "sourceUrl": {
+            "maxLength": 2560,
+            "type": "string"
+          }
+        },
+        "required": [
+          "id",
+          "sourceUrl",
+          "line",
+          "column"
+        ],
+        "type": "object"
+      },
+      "maxItems": 100,
+      "type": "array"
+    },
+    "callFrames": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "column": {
+            "maximum": 9007199254740991,
+            "minimum": -9007199254740991,
+            "type": "integer"
+          },
+          "functionName": {
+            "maxLength": 500,
+            "type": "string"
+          },
+          "line": {
+            "maximum": 9007199254740991,
+            "minimum": -9007199254740991,
+            "type": "integer"
+          },
+          "locals": {
+            "additionalProperties": {
+              "$ref": "#/definitions/JsonValue"
+            },
+            "propertyNames": {
+              "type": "string"
+            },
+            "type": "object"
+          },
+          "scopeNames": {
+            "items": {
+              "maxLength": 100,
+              "type": "string"
+            },
+            "maxItems": 50,
+            "type": "array"
+          },
+          "url": {
+            "maxLength": 2560,
+            "type": "string"
+          }
+        },
+        "required": [
+          "functionName",
+          "url",
+          "line",
+          "column",
+          "scopeNames",
+          "locals"
+        ],
+        "type": "object"
+      },
+      "maxItems": 50,
+      "type": "array"
+    },
+    "paused": {
+      "type": "boolean"
+    },
+    "reason": {
+      "anyOf": [
+        {
+          "maxLength": 500,
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    }
+  },
+  "required": [
+    "paused",
+    "reason",
+    "callFrames",
+    "breakpoints"
+  ],
+  "type": "object"
+}

addedOutput schema / definitions / JsonValue

Added value: +{
+  "allOf": [
+    {
+      "$ref": "#/definitions/__schema0"
+    }
+  ]
+}

changedOutput schema / definitions / __schema0 / anyOf

Previous value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "number"
-  },
-  {
-    "type": "boolean"
-  },
-  {
-    "type": "null"
-  },
-  {
-    "items": {
-      "$ref": "#/definitions/__schema0"
-    },
-    "type": "array"
-  },
-  {
-    "additionalProperties": {
-      "$ref": "#/definitions/__schema0"
-    },
-    "propertyNames": {
-      "type": "string"
-    },
-    "type": "object"
-  }
-]New value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "number"
+  },
+  {
+    "type": "boolean"
+  },
+  {
+    "type": "null"
+  },
+  {
+    "items": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/__schema0"
+        }
+      ]
+    },
+    "type": "array"
+  },
+  {
+    "additionalProperties": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/__schema0"
+        }
+      ]
+    },
+    "propertyNames": {
+      "type": "string"
+    },
+    "type": "object"
+  }
+]

removedOutput schema / properties / data / additionalProperties
```
Removed value: -false
```

addedOutput schema / properties / data / allOf

Added value: +[
+  {
+    "$ref": "#/definitions/DebuggerSnapshotOutput"
+  }
+]

removedOutput schema / properties / data / properties

Removed value: -{
-  "breakpoints": {
-    "items": {
-      "additionalProperties": false,
-      "properties": {
-        "column": {
-          "anyOf": [
-            {
-              "maximum": 9007199254740991,
-              "minimum": -9007199254740991,
-              "type": "integer"
-            },
-            {
-              "type": "null"
-            }
-          ]
-        },
-        "id": {
-          "maxLength": 500,
-          "type": "string"
-        },
-        "line": {
-          "maximum": 9007199254740991,
-          "minimum": -9007199254740991,
-          "type": "integer"
-        },
-        "sourceUrl": {
-          "maxLength": 2560,
-          "type": "string"
-        }
-      },
-      "required": [
-        "id",
-        "sourceUrl",
-        "line",
-        "column"
-      ],
-      "type": "object"
-    },
-    "maxItems": 100,
-    "type": "array"
-  },
-  "callFrames": {
-    "items": {
-      "additionalProperties": false,
-      "properties": {
-        "column": {
-          "maximum": 9007199254740991,
-          "minimum": -9007199254740991,
-          "type": "integer"
-        },
-        "functionName": {
-          "maxLength": 500,
-          "type": "string"
-        },
-        "line": {
-          "maximum": 9007199254740991,
-          "minimum": -9007199254740991,
-          "type": "integer"
-        },
-        "locals": {
-          "additionalProperties": {
-            "$ref": "#/definitions/__schema0"
-          },
-          "propertyNames": {
-            "type": "string"
-          },
-          "type": "object"
-        },
-        "scopeNames": {
-          "items": {
-            "maxLength": 100,
-            "type": "string"
-          },
-          "maxItems": 50,
-          "type": "array"
-        },
-        "url": {
-          "maxLength": 2560,
-          "type": "string"
-        }
-      },
-      "required": [
-        "functionName",
-        "url",
-        "line",
-        "column",
-        "scopeNames",
-        "locals"
-      ],
-      "type": "object"
-    },
-    "maxItems": 50,
-    "type": "array"
-  },
-  "paused": {
-    "type": "boolean"
-  },
-  "reason": {
-    "anyOf": [
-      {
-        "maxLength": 500,
-        "type": "string"
-      },
-      {
-        "type": "null"
-      }
-    ]
-  }
-}

removedOutput schema / properties / data / required

Removed value: -[
-  "paused",
-  "reason",
-  "callFrames",
-  "breakpoints"
-]

removedOutput schema / properties / data / type
```
Removed value: -"object"
```

Changed5 schema fields changedv0.7.0Sep 1, 2026

addedOutput schema / properties / data / additionalProperties
```
Added value: +false
```

removedOutput schema / properties / data / allOf

Removed value: -[
-  {
-    "$ref": "#/definitions/__schema0"
-  }
-]

addedOutput schema / properties / data / properties

Added value: +{
+  "breakpoints": {
+    "items": {
+      "additionalProperties": false,
+      "properties": {
+        "column": {
+          "anyOf": [
+            {
+              "maximum": 9007199254740991,
+              "minimum": -9007199254740991,
+              "type": "integer"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
+        "id": {
+          "maxLength": 500,
+          "type": "string"
+        },
+        "line": {
+          "maximum": 9007199254740991,
+          "minimum": -9007199254740991,
+          "type": "integer"
+        },
+        "sourceUrl": {
+          "maxLength": 2560,
+          "type": "string"
+        }
+      },
+      "required": [
+        "id",
+        "sourceUrl",
+        "line",
+        "column"
+      ],
+      "type": "object"
+    },
+    "maxItems": 100,
+    "type": "array"
+  },
+  "callFrames": {
+    "items": {
+      "additionalProperties": false,
+      "properties": {
+        "column": {
+          "maximum": 9007199254740991,
+          "minimum": -9007199254740991,
+          "type": "integer"
+        },
+        "functionName": {
+          "maxLength": 500,
+          "type": "string"
+        },
+        "line": {
+          "maximum": 9007199254740991,
+          "minimum": -9007199254740991,
+          "type": "integer"
+        },
+        "locals": {
+          "additionalProperties": {
+            "$ref": "#/definitions/__schema0"
+          },
+          "propertyNames": {
+            "type": "string"
+          },
+          "type": "object"
+        },
+        "scopeNames": {
+          "items": {
+            "maxLength": 100,
+            "type": "string"
+          },
+          "maxItems": 50,
+          "type": "array"
+        },
+        "url": {
+          "maxLength": 2560,
+          "type": "string"
+        }
+      },
+      "required": [
+        "functionName",
+        "url",
+        "line",
+        "column",
+        "scopeNames",
+        "locals"
+      ],
+      "type": "object"
+    },
+    "maxItems": 50,
+    "type": "array"
+  },
+  "paused": {
+    "type": "boolean"
+  },
+  "reason": {
+    "anyOf": [
+      {
+        "maxLength": 500,
+        "type": "string"
+      },
+      {
+        "type": "null"
+      }
+    ]
+  }
+}

addedOutput schema / properties / data / required

Added value: +[
+  "paused",
+  "reason",
+  "callFrames",
+  "breakpoints"
+]

addedOutput schema / properties / data / type
```
Added value: +"object"
```

First observedv0.5.0-next.0Aug 30, 2026

TDQS

C2.7/5.0

Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=false, destructiveHint=true, idempotentHint=false and openWorldHint=true, so the safety profile is covered structurally. The description adds no behavioral context beyond them — it does not say that resume continues execution and may trigger side effects, that stepping is a single-instruction advance, or that the tool only works while ExecutionPaused.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

One short sentence with no filler, front-loading the verb and the target. It is arguably under-specified rather than padded, which is a completeness problem rather than a structure one.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists so return values need not be explained, and annotations carry the safety profile. However, a debug-control mutation that requires a paused session and a sessionId omits all precondition and postcondition context, leaving the agent to guess the operational state required to call it.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must carry the load, but it says only 'resume or step'. The enum values (stepOver/stepInto/stepOut) are self-describing names, yet the description never distinguishes them, and sessionId is entirely unexplained. It falls short of compensating for the coverage gap.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description pairs a specific verb set (resume/step) with a specific resource (a paused local JavaScript target), which is enough to separate it from siblings like web_debug_evaluate or web_breakpoint_set. It does not explicitly name which sibling to prefer, but the action is unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no when-to-use guidance: it never states that the target must already be paused, that a valid sessionId from the session/breakpoint flow is required, or when to prefer stepping versus resuming. The agent gets the action semantics from the enum but nothing about prerequisites or alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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