Summary

Agents running on openai-codex/gpt-5.4 (or any openai-codex-responses API) crash silently with zero output when any MCP server is configured that exposes tools with no parameters (e.g. aws___list_regions).

The session immediately terminates with stopReason: "error" and 0 tokens consumed. From the user's perspective it looks like a model timeout or silent failure — nothing is surfaced in the UI.

Root Cause

The OpenAI Responses API requires all type: "object" tool schemas to include a properties field, even if empty. MCP tools with no parameters are typically defined as:

{ "type": "object" }

The API rejects this with:

Invalid schema for function 'aws___list_regions': In context=(), object schema missing properties.

This crashes the entire session — not just the offending tool call — before a single token is generated.

Two Affected Locations

1. @mariozechner/pi-ai → convertResponsesTools() (critical path)

// providers/openai-responses-shared.js
export function convertResponsesTools(tools, options) {
    const strict = options?.strict === undefined ? false : options.strict;
    return tools.map((tool) => ({
        type: "function",
        name: tool.name,
        description: tool.description,
        parameters: tool.parameters, // passed directly with no normalization
        strict,
    }));
}

Tool parameters are passed directly to the API with no schema normalization. Any type: "object" schema missing properties reaches the wire unchanged.

2. OpenClaw → normalizeToolParameters() (defence-in-depth)

The existing normalizer in auth-profiles-B5ypC5S-.js handles:

• type: "object" with properties → passes through ✅
• No type field but has properties → injects type: "object" ✅
• type: "object" without properties → falls through unchanged ❌

This gap means even if a fix is applied in the normalizer, the pi-ai layer bypasses it entirely.

Fix

In both locations, normalize { type: "object" } → { type: "object", properties: {} }:

// convertResponsesTools fix
if (parameters?.type === "object" && !("properties" in parameters)) {
    parameters = { ...parameters, properties: {} };
}

// normalizeToolParameters fix (additional branch)
if ("type" in schema && !("properties" in schema) && !Array.isArray(schema.anyOf) && !Array.isArray(schema.oneOf)) {
    return preserveToolMeta({ ...tool, parameters: applyProviderCleaning({ ...schema, properties: {} }) });
}

These are semantically identical in JSON Schema — { type: "object" } and { type: "object", properties: {} } both mean "accept any object". The change is safe for all other providers.

Impact

• All agents on openai-codex/gpt-5.4 with any no-parameter MCP tool configured fail completely
• Silent failure — looks like a model hang, not a schema error
• Affects any MCP server that exposes informational/query tools with no input parameters (common pattern)

Workaround

Applied a local patch to convertResponsesTools() in @mariozechner/pi-ai which resolves the issue. Verified working: agent spawns successfully, returns output, 0 tokens → 19k tokens after patch.