[Bug] 400 "Improperly formed request" + 404 on /chat/completions when using Kiro IDE with MCP tools

[hyeonho-p]

Environment

• CLIProxyAPI Version: 6.8.22-0-plus
• Client: Kiro IDE (macOS)
• Model: kiro-claude-sonnet-4-6

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Bug 1 (Critical): 400 — "Improperly formed request" when tools array is included

Description

When Kiro sends a request that includes a tools array (MCP tools like context7, sequential-thinking, filesystem, etc.), CLIProxyAPI returns HTTP 400 with:

{"message":"Improperly formed request.","reason":null}

Requests without tools work fine. This completely breaks MCP tool functionality.

Request details

URL: /v1/chat/completions
Method: POST
Content-Length: 27057
Model: kiro-claude-sonnet-4-6

Tools included in the failing request:

• context7__resolve-library-id
• context7__query-docs
• sequential-thinking__sequentialthinking
• filesystem__read_file, read_text_file, write_file, edit_file, etc.

Suspected cause

The proxy may not be correctly translating OpenAI-format tools schema to Claude API format before forwarding. The tools[].function.parameters structure or the overall payload size/structure is being rejected by the upstream Claude API.

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Bug 2: 404 — Missing /v1/ prefix in request URL

Description

In a separate case, the proxy sent a request to /chat/completions (without the /v1/ prefix), resulting in a 404.

URL: /chat/completions   ← missing /v1/
Method: POST
Response: 404

This appears to be a routing/base-path issue in the proxy configuration.

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Impact

Bug	Impact
400 (tools)	All MCP tool calls fail — core functionality broken
404 (path)	All requests fail when base path is misconfigured

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Notes

Both errors were captured from CLIProxyAPI error logs at:
~/Library/Application Support/Quotio/logs/

Happy to provide full log files if helpful.

[mumong]

same bug about using it, my claude code tolde me that it matters with how cpa deal with format bewten openai and claude code