docs: Add error categorization docs

[duwenxin99]

No description provided.

[gemini-code-assist]

Summary of Changes

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This pull request enhances the developer documentation by adding a new section dedicated to error handling within the Toolbox framework. The update clarifies how to categorize and implement different error types, ensuring robust agentic workflows and proper alignment with the Model Context Protocol. This will help developers understand and correctly apply error handling strategies for tools.

Highlights

• New Documentation Section: Added a comprehensive section on 'Tool Invocation & Error Handling' to DEVELOPER.md.
• Error Categorization: Introduced a clear distinction between 'Agent Error' (fixable by LLM) and 'Server Error' (requiring developer intervention), aligning with the Model Context Protocol (MCP).
• Implementation Guidelines: Provided guidelines for implementing Invoke() and ParseParams() methods to return util.ToolboxError, specifying when to use AgentError or ClientServerError.
• Code Example: Included a Go code example demonstrating how to correctly handle and return AgentError within an Invoke() method.

Changelog

• DEVELOPER.md
  • Added new documentation section 'Tool Invocation & Error Handling'.
  • Detailed error categorization into Agent Error and Server Error.
  • Provided implementation guidelines for Invoke() and ParseParams() methods.
  • Included a Go code example for error handling.

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[gemini-code-assist]

Code Review

This pull request adds important documentation on error handling within the MCP Toolbox. The new section clarifies the distinction between Agent and Server errors, which is crucial for building robust tools. I've identified a few areas in the new documentation that need correction to ensure accuracy and consistency with the existing codebase. Specifically, the example Invoke function has an incorrect signature, the error type names in the categorization table are wrong, and one of the implementation guidelines could be more precise. Please see my detailed comments for suggestions.

[github-actions]

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Summary

Status	Count
🔍 Total	45
✅ Successful	39
⏳ Timeouts	0
👻 Excluded	0
❓ Unknown	0
🚫 Errors	1
⛔ Unsupported	0

Errors per input

Errors in DEVELOPER.md

• [ERROR] https://play.dgraph.io/ | Network error: Connection failed. Check network connectivity and firewall settings (error sending request for url (https://play.dgraph.io/)): Connection failed. Check network connectivity and firewall settings

Full Github Actions output