mcp-json-yaml-toml

data_query

Read-onlyIdempotent

Extract specific data, filter content, or restructure JSON, YAML, and TOML files using yq expressions, without modifying the original file.

Instructions

Extract specific data, filter content, or transform structure without modification.

Use when you need to extract specific data, filter content, or transform the structure of a JSON, YAML, or TOML file without modifying it.

Output contract: Returns {"success": bool, "result": Any, "format": str, "file": str, ...}. Side effects: None (read-only). Failure modes: FileNotFoundError if file missing. ToolError if format disabled or query fails.

Input Schema

TableJSON Schema

Name	Required	Description
`cursor`	No	Pagination cursor from previous response (omit for first page)
`file_path`	Yes	Path to file
`expression`	Yes	yq expression to evaluate (e.g., '.name', '.items[]', '.data.users')
`output_format`	No	Output format (defaults to same as input file format)
`document_index`	No	Optional YAML document index for multi-document files (0-based)

Output Schema

TableJSON Schema

Name	Required	Description	Default
`file`	No
`format`	No
`result`	No
`success`	Yes
`advisory`	No
`paginated`	No
`nextCursor`	No
`schema_info`	No
`structure_summary`	No

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

Changed7 schema fields changedv0.10.0Jul 12, 2026

removedInput schema / $defs

Removed value: -{
-  "FormatType": {
-    "description": "Supported file format types for yq operations.",
-    "enum": [
-      "json",
-      "yaml",
-      "toml",
-      "xml",
-      "csv",
-      "tsv",
-      "props"
-    ],
-    "type": "string"
-  }
-}

addedInput schema / additionalProperties
```
Added value: +false
```

addedInput schema / properties / document_index

Added value: +{
+  "anyOf": [
+    {
+      "type": "integer"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional YAML document index for multi-document files (0-based)"
+}

changedInput schema / properties / output_format / anyOf

Previous value: -[
-  {
-    "$ref": "#/$defs/FormatType"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "description": "Supported file format types for yq operations.",
+    "enum": [
+      "json",
+      "yaml",
+      "toml",
+      "xml",
+      "csv",
+      "tsv",
+      "props"
+    ],
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedOutput schema / description

Added value: +"Response for data GET and data_query returns."

addedOutput schema / properties

Added value: +{
+  "advisory": {
+    "anyOf": [
+      {
+        "type": "string"
+      },
+      {
+        "type": "null"
+      }
+    ],
+    "default": null
+  },
+  "file": {
+    "anyOf": [
+      {
+        "type": "string"
+      },
+      {
+        "type": "null"
+      }
+    ],
+    "default": null
+  },
+  "format": {
+    "default": "",
+    "type": "string"
+  },
+  "nextCursor": {
+    "anyOf": [
+      {
+        "type": "string"
+      },
+      {
+        "type": "null"
+      }
+    ],
+    "default": null
+  },
+  "paginated": {
+    "default": false,
+    "type": "boolean"
+  },
+  "result": {
+    "default": null,
+    "title": "Result"
+  },
+  "schema_info": {
+    "anyOf": [
+      {
+        "properties": {
+          "name": {
+            "type": "string"
+          },
+          "source": {
+            "type": "string"
+          },
+          "url": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "name",
+          "url",
+          "source"
+        ],
+        "type": "object"
+      },
+      {
+        "type": "null"
+      }
+    ],
+    "default": null
+  },
+  "structure_summary": {
+    "anyOf": [
+      {
+        "type": "string"
+      },
+      {
+        "type": "null"
+      }
+    ],
+    "default": null
+  },
+  "success": {
+    "type": "boolean"
+  }
+}

addedOutput schema / required
```
Added value: +[
+  "success"
+]
```

First observedv1.0.0Jan 11, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Beyond annotations (readOnlyHint, idempotentHint, destructiveHint), the description adds output contract format, confirms no side effects, and lists failure modes (FileNotFoundError, ToolError). No contradiction with annotations.

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

Conciseness5/5

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

The description is concise with three clear sections: purpose, usage, and contract/behavior. Every sentence adds value, no fluff. Front-loaded with primary purpose.

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

Completeness5/5

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

Given the tool's complexity (5 params, 2 required, output schema present), the description fully covers purpose, usage, output contract, side effects, and failure modes. No gaps remain.

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

Parameters3/5

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

Schema coverage is 100% with detailed parameter descriptions. The description does not add significant meaning beyond the schema (e.g., mentions 'yq expression' and supported formats). Baseline 3 applies.

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

Purpose5/5

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

The description clearly states the tool extracts, filters, or transforms data without modification, using a specific verb and resource. It distinguishes from siblings like data_convert or data_merge by emphasizing read-only querying on JSON, YAML, TOML files.

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

Usage Guidelines4/5

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

The description explicitly states when to use the tool (extracting/filtering/transforming without modification) and provides output contract and failure modes. It lacks explicit when-not-to-use or alternative tools, but the context is clear.

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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