Generate server instructions in the Inventory

[tommaso-moro]

Summary

This PR moves server instructions generation from NewMCPServer into the Inventory pattern, so instructions are computed at inventory build time rather than server creation time.

Changes

• Added instructions field to Inventory struct with Instructions() getter method
• Added InstructionsFunc field to ToolsetMetadata allowing each toolset to define its own instructions
• Added WithServerInstructions() builder method that enables instruction generation during Build()
• Created pkg/github/toolset_instructions.go with instruction functions for each toolset (context, issues, pull_requests, discussions, projects)
• Moved instruction generation to pkg/inventory/instructions.go , which first adds base instructions and then iterates over toolsets and calls their InstructionsFunc
• Updated both STDIO and HTTP paths to use .WithServerInstructions() when building inventory
• Updated NewMCPServer to use inventory.Instructions() instead of generating instructions inline

Testing

• Unit tests moved to pkg/inventory/instructions_test.go
• Manually verified STDIO server with/without .WithServerInstructions()
• Manually verified HTTP server includes instructions in initialize response

Demo

Screen.Recording.2026-01-22.at.12.46.46.mov

Why

This aligns with the architectural direction where the Inventory holds all pre-computed configuration, and the MCP server receives a fully-configured inventory rather than creating one itself. Instructions are generated based on the resolved enabled toolsets (after processing "default", "all" keywords, etc.)

MCP impact

• No tool or API changes
• Tool schema or behavior changed
• New tool added

Prompts tested (tool changes only)

Security / limits

• No security or limits impact
• Auth / permissions considered
• Data exposure, filtering, or token/size limits considered

Tool renaming

• I am renaming tools as part of this PR (e.g. a part of a consolidation effort)
  • I have added the new tool aliases in deprecated_tool_aliases.go
• I am not renaming tools as part of this PR

Note: if you're renaming tools, you must add the tool aliases. For more information on how to do so, please refer to the official docs.

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

Docs

• Not needed
• Updated (README / docs / examples)

Note

The linter in the CI is failing due to pre-existing issues in the work-in-progress base branch http-stack-2

[Copilot]

Pull request overview

This PR refactors the server instructions generation logic by moving it from the pkg/github package to the pkg/inventory package, improving the separation of concerns.

Changes:

• Moved GenerateInstructions and related functions from pkg/github to pkg/inventory
• Made instruction generation opt-in via a new WithServerInstructions() builder method
• Updated both stdio and HTTP server initialization to use the new inventory-based instructions

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/inventory/registry.go	Added instructions field to Inventory struct and Instructions() getter method
pkg/inventory/instructions.go	Moved from pkg/github to pkg/inventory with package change and function visibility adjustments
pkg/inventory/instructions_test.go	Moved from pkg/github to pkg/inventory with type updates from []string to []ToolsetID
pkg/inventory/builder.go	Added WithServerInstructions() builder method and instruction generation in Build()
pkg/http/handler.go	Added WithServerInstructions() call in DefaultInventoryFactory
pkg/github/server.go	Removed local instruction generation logic, now uses inventory.Instructions()
internal/ghmcp/server.go	Added WithServerInstructions() call to inventory builder chain

[tommaso-moro]

Closing because I ended up doing this in this PR instead: #1869