list_root_fields
Retrieve available top-level query, mutation, or subscription fields for a Hasura GraphQL endpoint to enable schema discovery and dynamic interaction with the API.
Instructions
Lists the available top-level query, mutation, or subscription fields...
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| fieldType | No | Optional. Filter by 'QUERY'... |
Input Schema (JSON Schema)
{
"$schema": "http://json-schema.org/draft-07/schema#",
"additionalProperties": false,
"properties": {
"fieldType": {
"description": "Optional. Filter by 'QUERY'...",
"enum": [
"QUERY",
"MUTATION",
"SUBSCRIPTION"
],
"type": "string"
}
},
"type": "object"
}
Implementation Reference
- src/index.ts:247-280 (registration)Registers the MCP tool 'list_root_fields' with description, input schema, and handler function.server.tool( "list_root_fields", "Lists the available top-level query, mutation, or subscription fields...", { fieldType: z.enum(["QUERY", "MUTATION", "SUBSCRIPTION"]).optional().describe("Optional. Filter by 'QUERY'...") }, async ({ fieldType }) => { console.log(`[INFO] Executing tool 'list_root_fields', filtering by: ${fieldType || 'ALL'}`); try { const schema = await getIntrospectionSchema(); let fields: IntrospectionField[] = []; if ((!fieldType || fieldType === "QUERY") && schema.queryType) { const queryRoot = schema.types.find(t => t.name === schema.queryType?.name) as IntrospectionObjectType | undefined; fields = fields.concat(queryRoot?.fields || []); } if ((!fieldType || fieldType === "MUTATION") && schema.mutationType) { const mutationRoot = schema.types.find(t => t.name === schema.mutationType?.name) as IntrospectionObjectType | undefined; fields = fields.concat(mutationRoot?.fields || []); } if ((!fieldType || fieldType === "SUBSCRIPTION") && schema.subscriptionType) { const subscriptionRoot = schema.types.find(t => t.name === schema.subscriptionType?.name) as IntrospectionObjectType | undefined; fields = fields.concat(subscriptionRoot?.fields || []); } const fieldInfo = fields.map(f => ({ name: f.name, description: f.description || "No description.", })).sort((a, b) => a.name.localeCompare(b.name)); return { content: [{ type: "text", text: JSON.stringify(fieldInfo, null, 2) }] }; } catch (error: any) { console.error(`[ERROR] Tool 'list_root_fields' failed: ${error.message}`); throw error; } } );
- src/index.ts:253-279 (handler)Executes the tool by fetching the GraphQL introspection schema, collecting fields from query/mutation/subscription root types based on optional fieldType filter, formats name and description, sorts, and returns as JSON.async ({ fieldType }) => { console.log(`[INFO] Executing tool 'list_root_fields', filtering by: ${fieldType || 'ALL'}`); try { const schema = await getIntrospectionSchema(); let fields: IntrospectionField[] = []; if ((!fieldType || fieldType === "QUERY") && schema.queryType) { const queryRoot = schema.types.find(t => t.name === schema.queryType?.name) as IntrospectionObjectType | undefined; fields = fields.concat(queryRoot?.fields || []); } if ((!fieldType || fieldType === "MUTATION") && schema.mutationType) { const mutationRoot = schema.types.find(t => t.name === schema.mutationType?.name) as IntrospectionObjectType | undefined; fields = fields.concat(mutationRoot?.fields || []); } if ((!fieldType || fieldType === "SUBSCRIPTION") && schema.subscriptionType) { const subscriptionRoot = schema.types.find(t => t.name === schema.subscriptionType?.name) as IntrospectionObjectType | undefined; fields = fields.concat(subscriptionRoot?.fields || []); } const fieldInfo = fields.map(f => ({ name: f.name, description: f.description || "No description.", })).sort((a, b) => a.name.localeCompare(b.name)); return { content: [{ type: "text", text: JSON.stringify(fieldInfo, null, 2) }] }; } catch (error: any) { console.error(`[ERROR] Tool 'list_root_fields' failed: ${error.message}`); throw error; } }
- src/index.ts:250-252 (schema)Zod schema for input parameters: optional 'fieldType' enum to filter by QUERY, MUTATION, or SUBSCRIPTION.{ fieldType: z.enum(["QUERY", "MUTATION", "SUBSCRIPTION"]).optional().describe("Optional. Filter by 'QUERY'...") },