Add instructions to server info

[0xKoller]

No description provided.

[linear]

XMCP-408 Add support for `instructions` according to MCP standart

[vercel]

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Project	Deployment	Actions	Updated (UTC)
xmcp-website	Ready	Preview, Comment	Mar 17, 2026 9:27pm

[github-actions]

Rspack Bundle Analysis

Build	Assets	Total Size (MB)	Build Time
Main Compiler	4	6.32	5.18s
Runtime Compiler	6	5.35	6.00s

Main Compiler

Source: stats-main.json

Asset	Chunk	Size (KB)	Size (MB)
cli.js	cli	6009.40	5.87
index.js	index	368.80	0.36
cloudflare.js	cloudflare	81.70	0.08
detached-flush.js	detached-flush	15.18	0.01

Total emitted JS: 6.32 MB

Runtime Compiler

Source: stats-runtime.json

Asset	Chunk	Size (KB)	Size (MB)
http.js	http	1305.70	1.28
adapter-nestjs.js	adapter-nestjs	1281.97	1.25
adapter-nextjs.js	adapter-nextjs	1276.39	1.25
adapter-express.js	adapter-express	1274.28	1.24
stdio.js	stdio	343.31	0.34
headers.js	headers	1.33	0.00

Total emitted JS: 5.35 MB

Package Footprint (npm pack + npm install)

Item	Size (KB)	Size (MB)
Tarball (.tgz)	4622.10	4.51
dist/	12011.22	11.73
node_modules/	101024.96	98.66
dist + node_modules	113036.18	110.39

[greptile-apps]

Greptile Summary

This PR adds an optional instructions field to the xmcp server template configuration, which is forwarded to MCP clients in the initialize response so they can include it in the system prompt. It also fixes an existing divergence where the Next.js adapter's initializeMcpServer() was creating McpServer directly (bypassing createServer()), by refactoring it to delegate to createServer() — the same pattern already used by the Express and NestJS adapters.

• template.ts: adds instructions: z.string().optional() with thorough JSDoc documentation.
• injection.ts: conditionally injects SERVER_INSTRUCTIONS at build time when instructions are provided, consistent with how other config variables (e.g., SERVER_INFO) are handled.
• server.ts: reads INJECTED_INSTRUCTIONS using a safe typeof guard (necessary since the variable may not be injected), and passes it to McpServer options in createServer().
• server-lifecycle.ts (Next.js adapter): initializeMcpServer() is reduced to a single return createServer() call, eliminating the duplicated setup logic and ensuring instructions is correctly applied for Next.js users.
• Documentation in server-info.mdx is updated with a clear usage example and guidance on what the field should and should not contain.

Confidence Score: 5/5

• This PR is safe to merge — the change is well-scoped, consistent with existing patterns, and the previously identified Next.js adapter divergence has been correctly resolved.
• All adapters (Next.js, NestJS, Express) now route through a single createServer() call, the injected-variable pattern is consistent with the rest of the codebase, the typeof guard on SERVER_INSTRUCTIONS correctly handles the case when no instructions are configured, and the documentation is clear and accurate.
• No files require special attention.

Important Files Changed

Filename	Overview
packages/xmcp/src/runtime/utils/server.ts	Adds INJECTED_INSTRUCTIONS module-level variable and passes it to McpServer options inside createServer(); logic is sound and consistent with other injected globals.
packages/xmcp/src/runtime/adapters/nextjs/handler/server-lifecycle.ts	Refactored initializeMcpServer() to delegate entirely to createServer(), fixing the previously-identified divergence where the Next.js adapter bypassed instructions support.
packages/xmcp/src/compiler/config/injection.ts	Conditionally injects SERVER_INSTRUCTIONS when templateConfig.instructions is truthy; consistent with the pattern used for other injected variables.
packages/xmcp/src/compiler/config/schemas/template.ts	Adds instructions: z.string().optional() with thorough JSDoc; no issues.
apps/website/content/docs/configuration/server-info.mdx	Documentation updated with a clear instructions section, usage example, and guidance on what the field should contain.

_{Last reviewed commit: b644384}

[0xKoller]

@greptileai