Add PlanetScale external plugin

[SimeonGriggs]

Add PlanetScale external plugin

Adds PlanetScale as an external plugin in plugins/external.json, sourced from planetscale/vscode-agent-plugin.

What it provides

• MCP Server: Authenticated access to PlanetScale organizations, databases, branches, schema, and query performance Insights via the hosted PlanetScale MCP endpoint (https://mcp.pscale.dev/mcp/planetscale). No local setup required.
• 4 Database Skills:
  • mysql — Schema design, indexing, query tuning, transactions, and operations for MySQL/InnoDB
  • postgres — Best practices, query optimization, MVCC, connection pooling, and PlanetScale-specific Postgres tooling
  • vitess — VSchema, sharding, vindexes, online DDL, and VReplication for PlanetScale Vitess databases
  • neki — Sharding readiness for PostgreSQL (PlanetScale's sharded Postgres)

Checklist

• Added entry to plugins/external.json
• Ran npm run build to regenerate marketplace.json
• PR targets staged branch

Source repository

https://github.com/planetscale/vscode-agent-plugin

[aaronpowell]

At this point in time we are only supporting external plugins from Microsoft and GitHub orgs, not the broader community. With #969 the Contributing guide has been updated to reflect this policy.

[SimeonGriggs]

At this point in time we are only supporting external plugins from Microsoft and GitHub orgs, not the broader community. With #969 the Contributing guide has been updated to reflect this policy.

Thanks @aaronpowell, but I'm a little confused. Here you're saying only Microsoft and GitHub organizations can be accepted, but the announcement says you're open to external contributions from other services?

Though the MCP server in this plugin is PlanetScale-specific, the Database Skills package is deliberately generic and useful to any developer who is looking to improve their database code with any provider.

Would you accept an updated submission that only includes those skills?

[aaronpowell]

Happy to have submissions around commercial products where they are things like skills that uplift agents to support them, but they would need to be skills/agents/etc. that live within this repo rather than via remote plugins. Remote plugins are a different situation as the marketplace (us) have no visibility on what we're delivering and thus can pose a compliance risk.

Mostly, the policy described in #968 is more to combat the rise in submissions that are low-quality paid "services" that are little more than proxies to other systems and thus provide questionable value. PlanetScale doesn't fit that categorisation, so we'd be happy to have contributions to support them in here, but they would need to live in the repo.