Fully implement MCP Spec 2025-06-18

[crivetimihai]

Closes #708 #234 #1285

#	Status	Issue	Priority	File(s)	Description
1	[x]	ImageContent fixed	🔴 Critical	models.py:126-140	Now uses str; extends BaseModelWithConfigDict; has camelCase conversion
2	[x]	CallToolResult fixed	🔴 Critical	models.py:553-572	Returns isError; has structuredContent; extends BaseModelWithConfigDict
3	[x]	ResourceContents fixed	🔴 Critical	models.py:143-174	Returns mimeType; spec-compliant TextResourceContents and BlobResourceContents
4	[x]	resources/subscribe+unsubscribe added	🔴 Critical	main.py:3524-3543	Both now in JSON-RPC; were REST-only
5	[x]	Pagination implemented	✅ Complete	tool/resource/prompt services, main.py:3530-3609	Cursor-based pagination with nextCursor support
6	[x]	AudioContent created	🟡 High	models.py:195-210	Class created with base64 data, mimeType, annotations
7	[x]	ResourceLink created	🟡 High	models.py:725-735	Class created extending Resource
8	[x]	EmbeddedResource created	🟡 High	models.py:738-755	Class created with resource union type
9	[x]	Annotations interface created	🟡 High	models.py:94-112	Structured annotations with audience, priority, lastModified
10	[x]	ToolAnnotations created	🟡 High	models.py:115-136	Tool hints with all required fields
11	[x]	TextResourceContents created	🟡 High	models.py:157-164	Spec-compliant resource content type created (item 3)
12	[x]	BlobResourceContents created	🟡 High	models.py:167-174	Spec-compliant resource content type created (item 3)
13	[x]	ContentBlock union created	🟡 High	models.py:758-766	Union of TextContent, ImageContent, AudioContent, ResourceLink, EmbeddedResource
14	[x]	PromptMessage created	🟡 High	models.py:394-411	Distinct from SamplingMessage; extends BaseModelWithConfigDict
15	[x]	_meta added	🟠 High	schemas.py + models.py	Added to ToolRead, ResourceRead, PromptRead, Resource, ResourceTemplate, Prompt, Root
16	[x]	title field added	🟠 High	schemas.py	ResourceRead and PromptRead now have title field
17	[x]	annotations added	🟠 High	schemas.py:1808 + models.py:722	ResourceRead and ResourceTemplate now have annotations
18	[x]	TextContent fixed	🟢 Medium	models.py:140-163	Now extends BaseModelWithConfigDict with annotations
19	[x]	Completions advertised	🟢 Medium	session_registry.py:1249	Capability now advertised in ServerCapabilities
20	[x]	JSONContent removed	🟢 Medium	models.py:267	Removed unused dead code from codebase
21	[x]	PromptArgument completed	🟠 High	models.py:507-523	Now extends BaseModelWithConfigDict with title and _meta
22	[x]	completion/complete added	🔴 Critical	main.py:3577-3579	Now in /rpc; was REST-only
23	[x]	resources/templates/list implemented	🟡 High	main.py:3579-3582	Now in /rpc; was stub returning {}
24	[x]	PROTOCOL_VERSION updated	🟡 High	.env.example:101, config.py:166	Updated to "2025-06-18"
25	[x]	sampling/createMessage added	🔴 Critical	main.py:3569-3571	Now in /rpc; was REST-only
26	[x]	roots/list implemented	🔴 Critical	main.py:3560-3563, session_registry.py:1250	Added roots/list alongside legacy list_roots; advertised capability
27	[x]	elicitation/* fully implemented	✅ Complete	main.py:3622-3726, services/elicitation_service.py, session_registry.py:1263-1314	Full implementation with capability tracking
28	[x]	logging/setLevel added	🔴 Critical	main.py:3583-3587	Now in /rpc; was REST-only
29	[x]	notifications/* added	🔴 Critical	main.py:3567-3588	initialized/cancelled/message now in /rpc; was REST-only
30	[~]	Progress notifications	🟢 Optional	N/A	Optional feature - Spec says "MAY send" - not required
31	[~]	Cancellation handling	🟢 Optional	main.py:3595-3600	Optional feature - Spec says "SHOULD stop" - logging is compliant
32	[x]	MCP-Protocol-Version header	🟢 Medium	middleware/protocol_version.py	Middleware validates header per spec
33	[x]	Extra fields	✅ Not an issue	N/A	Compatible by design - MCP allows extra fields

[madhav165]

Noticed some issues while testing with MCP inspector.

1. initialize rpc request not returning elicitation in capabilities
2. Getting different capabilities for streamablehttp and sse endpoints - sse has logging and completions capabilities not being returned in streamablehttp
3. resources/templates/list rpc call only working in sse, giving an error in streamablehttp
4. resources/read rpc call working in streamablehttp, but not in sse. But, streamablehttp also returning empty contents for resources.

[crivetimihai]

fix: MCP spec compliance and transport parity

• Remove invalid 'roots' field from ServerCapabilities per MCP spec 2025-06-18
  Server capabilities should only include: prompts, resources, tools, logging,
  completions, and experimental. roots is a client capability, not server.

• Add missing handlers to streamablehttp transport for feature parity with SSE/RPC:

  • list_resource_templates: Enables resources/templates/list via streamablehttp
  • set_logging_level: Adds logging/setLevel support
  • completion: Provides argument completion suggestions
    This ensures both transports advertise the same capabilities.

• Fix resources/read in streamablehttp to return proper content:

  • Return blob content for binary resources
  • Return text content for text resources
  • Return empty string (not empty list) on errors for correct type signature
  • Fixes empty contents issue reported via MCP inspector

• Update tests to match corrected return type (str/bytes instead of list)

Closes issues found during MCP inspector testing:

1. Missing elicitation in capabilities (not needed - client capability)
2. Different capabilities between streamablehttp and SSE (now fixed)
3. resources/templates/list not working in streamablehttp (now fixed)
4. resources/read returning empty contents (now fixed)

[crivetimihai]

@madhav165 - please check again and make any necessary changes. I've rebased and made the fixes above.