[Bug] NetBox MCP tools fail JSON parsing despite valid API response #128

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lmiranda · 2026-01-23T22:29:21Z

lmiranda commented

2026-01-23 22:29:21 +00:00

Diagnostic Report

Generated: 2026-01-23T22:30:00Z
Command Tested: /cmdb-assistant:cmdb-device (device listing)
Reporter: Claude Code via /debug-report
Plugin: cmdb-assistant

Problem Summary

All NetBox MCP tools fail with JSON parsing errors, even though the NetBox API returns valid JSON responses.

Error Message:

Invalid JSON response from NetBox: Expecting value: line 8 column 1 (char 7). Status code: 200, Content length: 3511 bytes

Evidence

Test	Method	Result
dcim_list_devices	MCP Tool	FAIL - JSON parse error
dcim_list_sites	MCP Tool	FAIL - JSON parse error
/api/dcim/devices/	Direct curl	PASS - Valid JSON
/api/dcim/sites/	Direct curl	PASS - Valid JSON

Key Observations

NetBox returns HTTP 200 with valid content
Same error position (line 8 column 1) on all failures
Direct curl with same credentials works perfectly
Content length shows data is being returned (3511 bytes)

Hypothesis

The MCP server HTTP client or JSON parser is likely:

Reading HTTP headers as part of the response body
Not handling chunked transfer encoding properly
Having a streaming/buffer issue before parsing

Additional Issue

Service creation API requires parent_object_type + parent_object_id instead of device field, suggesting possible outdated API schema.

Suggested Investigation

Check HTTP client response handling in mcp-servers/netbox/
Verify chunked encoding handling
Check if headers are being included in body
Verify NetBox API version compatibility

Workaround

Use direct curl calls instead of MCP tools.

Generated by /debug-report

## Diagnostic Report **Generated**: 2026-01-23T22:30:00Z **Command Tested**: /cmdb-assistant:cmdb-device (device listing) **Reporter**: Claude Code via /debug-report **Plugin**: cmdb-assistant ## Problem Summary All NetBox MCP tools fail with JSON parsing errors, even though the NetBox API returns valid JSON responses. **Error Message**: ``` Invalid JSON response from NetBox: Expecting value: line 8 column 1 (char 7). Status code: 200, Content length: 3511 bytes ``` ## Evidence | Test | Method | Result | |------|--------|--------| | dcim_list_devices | MCP Tool | FAIL - JSON parse error | | dcim_list_sites | MCP Tool | FAIL - JSON parse error | | /api/dcim/devices/ | Direct curl | PASS - Valid JSON | | /api/dcim/sites/ | Direct curl | PASS - Valid JSON | ## Key Observations 1. NetBox returns HTTP 200 with valid content 2. Same error position (line 8 column 1) on all failures 3. Direct curl with same credentials works perfectly 4. Content length shows data is being returned (3511 bytes) ## Hypothesis The MCP server HTTP client or JSON parser is likely: 1. Reading HTTP headers as part of the response body 2. Not handling chunked transfer encoding properly 3. Having a streaming/buffer issue before parsing ## Additional Issue Service creation API requires parent_object_type + parent_object_id instead of device field, suggesting possible outdated API schema. ## Suggested Investigation 1. Check HTTP client response handling in mcp-servers/netbox/ 2. Verify chunked encoding handling 3. Check if headers are being included in body 4. Verify NetBox API version compatibility ## Workaround Use direct curl calls instead of MCP tools. --- Generated by /debug-report

lmiranda added the Component/Backend Type/Bug labels 2026-01-23 22:29:21 +00:00

lmiranda commented

2026-01-23 22:53:23 +00:00

Closing as duplicate of #126. See PR #132 for the fix.

lmiranda closed this issue

2026-01-23 22:53:34 +00:00

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Reference: personal-projects/leo-claude-mktplace#128