ruvnet/RuView · error · McpError

-32602

-32602

Error message

Invalid arguments for tool "${rawName}": ${parsed.error.message}

What it means

The RuView MCP server (tools/ruview-mcp/src/index.ts) validates every tool call's arguments with the tool's zod schema via schema.safeParse(args ?? {}). On failure it throws McpError(ErrorCode.InvalidParams), JSON-RPC code -32602, with the zod validation message embedded, so the client gets a structured error instead of tool output.

Source

Thrown at tools/ruview-mcp/src/index.ts:294

    if (!tool) {
      return {
        content: [
          {
            type: "text" as const,
            text: JSON.stringify({
              ok: false,
              error: `Unknown tool "${rawName}". Available tools: ${TOOLS.map((t) => t.name).join(", ")}`,
            }),
          },
        ],
        isError: true,
      };
    }

    const parsed = tool.schema.safeParse(args ?? {});
    if (!parsed.success) {
      throw new McpError(
        ErrorCode.InvalidParams,
        `Invalid arguments for tool "${rawName}": ${parsed.error.message}`
      );
    }

    try {
      const result = await tool.handler(parsed.data, config);
      return {
        content: [
          {
            type: "text" as const,
            text: JSON.stringify(result, null, 2),
          },
        ],
      };
    } catch (e: unknown) {
      if (e instanceof McpError) throw e; // propagate typed errors unchanged
      const message = e instanceof Error ? e.message : String(e);

View on GitHub (pinned to 4685618388)

Solutions

1. Read the tool's inputSchema from the tools/list response and shape arguments to exactly that schema.
2. Fix the specific field named in the zod message embedded in the error text (it lists the path and the violated constraint).
3. Make sure the MCP client sends arguments as a JSON object (not a stringified payload), and match client/server versions.

Example fix

// before
client.callTool({ name: 'ruview_guidance', arguments: JSON.stringify({ topic: 'overview', limit: 100 }) })
// after
client.callTool({ name: 'ruview_guidance', arguments: { topic: 'overview', limit: 10 } })

// Fetch and enforce the server's own schema before calling
const { tools } = await client.listTools();
const tool = tools.find((t) => t.name === 'ruview_guidance');
// shape args strictly from tool.inputSchema (types, enums, min/max), e.g.:
const args = { topic: 'overview', limit: Math.min(20, Math.max(1, Number(rawLimit) || 20)) };

try {
  const res = await client.callTool({ name: 'ruview_guidance', arguments: args });
} catch (e) {
  if (e?.code === -32602 || /Invalid arguments for tool/.test(e?.message ?? '')) {
    // e.message embeds the zod path + violated constraint; fix that field, do not retry unchanged
    throw new Error(`schema violation calling ruview_guidance: ${e.message}`);
  }
  throw e;
}

When it happens

Trigger: Calling a ruview MCP tool with arguments that violate its schema: wrong types (limit as string), out-of-range values (ruview_guidance with limit 100), missing required fields, unknown tool-specific keys, or args serialized as a JSON string instead of a JSON object.

Common situations: Client/server schema drift after upgrading one side; hand-rolled MCP clients that pass arguments: JSON.stringify(payload); agents guessing parameter names; empty-string vs missing optional fields.

Related errors

• brain corpus exceeds 1000 records
• command must be a non-empty string
• args must be an array of strings
• timeoutMs must be a safe integer between 1000 and 1800000
• maxOutputBytes must be a positive safe integer

AI-assisted analysis of ruvnet/RuView@4685618388 (2026-08-16). Data as JSON: /api/errors/7998db63a18bf2b6. Report an issue: GitHub.