Missing JSON schema key intermittently

[zhabiba24]

What happened?

After building an MCP server following the anthropic reference implementation https://github.com/modelcontextprotocol/rust-sdk

When using this server in gemini CLI on first MCP call of a tool I almost always see this error

no schema with key or ref "https://json-schema.org/draft/2020-12/schema"

Then it goes away, which suggests this is something to do with gemini CLI having issues working with this flavour of JSON schema

What did you expect to happen?

Shouldn't get this error when the spec is valid and it goes away on subsequent invocations

Client information

Client Information

Run gemini to enter the interactive CLI, then run the /about command.

> /about
About Gemini CLI                                                                                                                                                                                                 │
│                                                                                                                                                                                                                  │
│ CLI Version                                                              0.25.0                                                                                                                                  │
│ Git Commit                                                               eb8834341                                                                                                                               │
│ Model                                                                    gemini-3-flash-preview                                                                                                                  │
│ Sandbox                                                                  no sandbox                                                                                                                              │
│ OS                                                                       darwin                                                                                                                                  │
│ Auth Method                                                              OAuth                                                                                                                                   │

Login information

Google account

Anything else we need to know?

No response

[bluedevil947]

+1 also seeing this error when working with Directus MCP. When gemini tries to use this MCP server it throws an error:
no schema with key or ref "https://json-schema.org/draft/2020-12/schema"

Tested gemini-cli version is 0.27.2
I just installed 0.28.0-preview.2 and it works so probably will be fixed in new release.

It looks like some calls work, some throw an error:

╭─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ x  collections (directus MCP Server) {"collection":"agent_logs","action":"delete"}                                      │
│                                                                                                                         │
│ params must NOT have additional properties                                                                              │
│                                                                                                                         │
│ x  collections (directus MCP Server) {"collection":"agent_sessions","action":"delete"}                                  │
│                                                                                                                         │
│ params must NOT have additional properties                                                                              │
│                                                                                                                         │
│ x  collections (directus MCP Server) {"collection":"ai_prompts","action":"delete"}                                      │
│                                                                                                                         │
│ params must NOT have additional properties                                                                              │
│                                                                                                                         │
│ x  collections (directus MCP Server) {"action":"delete","collection":"projects"}                                        │
│                                                                                                                         │
│ params must NOT have additional properties                                                                              │
╰──────────────────────────────────────────────

[achaljhawar]

/assign

[gemini-cli]

👋 @achaljhawar, thanks for your interest in this issue! We're reserving self-assignment for issues that have been marked with the help wanted label. Feel free to check out our list of issues that need attention.

[cocosheng-g]

Triage Summary

This bug report regarding the `` keyword causing intermittent failures in MCP tools is valid. The community PR (#21963) cleanly removes this metadata property for API compatibility while maintaining local validation. Categorized as Help-wanted.

@achaljhawar, apologies! It looks like your PR #21963 was incorrectly closed by our bot. I have reopened it and assigned this issue to you. Would you like to continue working on it?