🐛 Bug-fix PR

📌 Summary

MCP servers often include tools whose description fields contain Markdown syntax (e.g. > quoted text blockquotes, tokens, pipe characters in shell command examples). In v0.9.0 these descriptions registered without error. In v1.0.0.Beta2 a forbidden_patterns check was added to ToolCreate.validate_description in schemas.py that rejects descriptions containing &&, ;, ||, $(, |, > , or < . Unlike the similar validation in validators.py (which honours settings.validation_strict), this Pydantic validator is hardcoded — it raises unconditionally regardless of VALIDATION_STRICT, JSON_SCHEMA_VALIDATION_STRICT, or EXPERIMENTAL_VALIDATE_IO being set to false.

The result is that setting these environment variables has no effect on the registration error, contrary to documented expectations and to v0.9.0 behaviour.

Closes #3711

VALIDATION_STRICT=true:

VALIDATION_STRICT=false:

🔁 Reproduction Steps

1. Start an MCP server that exposes a tool whose description contains any of: &&, ;, ||, $(, |, > , < .
   Example description: "Search FICO product documentation > returns results" or "> Lists available options".
2. Register that server in ContextForge (v1.0.0.Beta2+).
3. Observe the error:

   All 1 tools failed validation. First error: Validation failed for tool 'search':
   [{'type': 'value_error', 'loc': ('description',),
     'msg': "Value error, Description contains unsafe characters: '> '", ...}]
   

4. Set VALIDATION_STRICT=false, JSON_SCHEMA_VALIDATION_STRICT=false, and EXPERIMENTAL_VALIDATE_IO=false.
5. Restart ContextForge and retry — the error persists unchanged (confirms env vars are ignored).

🐞 Root Cause

File: mcpgateway/schemas.py, ToolCreate.validate_description, lines 488–493

# Note: backticks (`) are allowed as they are commonly used in Markdown
# for inline code examples in tool descriptions
forbidden_patterns = ["&&", ";", "||", "$(", "|", "> ", "< "]
for pat in forbidden_patterns:
    if pat in v:
        raise ValueError(f"Description contains unsafe characters: '{pat}'")

This check:

• Is present only in ToolCreate.validate_description. ToolUpdate and all other schema validators (Resource, Prompt, Gateway, Server, A2AAgent, Team…) do not have it.
• Is hardcoded — settings.validation_strict is imported in schemas.py (line 43) but never consulted here.
• Runs at Pydantic validation time, before any middleware or db-layer validation, so EXPERIMENTAL_VALIDATE_IO (which toggles ValidationMiddleware) and JSON_SCHEMA_VALIDATION_STRICT (which toggles db-level JSON Schema validation) are both irrelevant to this code path.
• VALIDATION_STRICT is the correct setting to control this, as it is already used in validate_shell_parameter and validate_sql_parameter in validators.py for the same purpose.

💡 Fix Description

Wrap the raise with a settings.validation_strict guard:

# Note: backticks (`) are allowed as they are commonly used in Markdown
# for inline code examples in tool descriptions
forbidden_patterns = ["&&", ";", "||", "$(", "|", "> ", "< "]
for pat in forbidden_patterns:
    if pat in v:
        if settings.validation_strict:
            raise ValueError(f"Description contains unsafe characters: '{pat}'")
        logger.warning("Description contains potentially unsafe characters: '%s' (VALIDATION_STRICT=false, proceeding)", pat)
        break

🧪 Verification

📐 MCP Compliance (if relevant)

• Matches current MCP spec
• No breaking change to MCP clients

Checklist

• Code formatted (make black isort pre-commit)
• No secrets/credentials committed