Bug Description

After updating to OpenClaw 2026.3.28, all sub-agents (and sometimes main agent) fail with:

HTTP 400: tools.27.custom.input_schema: JSON schema is invalid. It must match JSON Schema draft 2020-12

The error occurs when any tool is invoked (e.g. read, file operations). The error is consistent and blocks all tool use.

Steps to Reproduce

1. Create a sub-agent with its own workspace (e.g. front-02)
2. Ask the sub-agent to read any file
3. Agent responds with HTTP 400 and the JSON schema error above

Expected Behavior

Tool calls should work normally.

Additional Context

• OpenClaw version: 2026.3.28 (f9b1079)
• Affects multiple agents: front-02 and potentially main agent
• Related known issue: [Bug]: HTTP 400: tools.27.custom.input_schema: JSON schema is invalid. It must match JSON Schema draft #29416 (patternProperties with regex causing schema invalid)
• Error message suggests a tool schema contains patternProperties: { "^(.*)$": {} } or similar which is incompatible with JSON Schema draft 2020-12

Questions

1. Is there a known fix or workaround?
2. Can OpenClaw provide a way to validate/fix tool schemas on startup?
3. Is there a way to identify which tool (index 27) is causing the issue?