Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Appearance settings

Allow Prompt/Sampling Messages to contain multiple content blocks. #198

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
evalstate wants to merge 11 commits into from
Closed

Allow Prompt/Sampling Messages to contain multiple content blocks. #198

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
11 commits
Select commit Hold shift + click to select a range
8baf498
switched prompt/sampling messages to array content blocks
evalstate Mar 13, 2025
eb4ad9a
Merge branch 'main' into feat/message-content-arrays
evalstate Apr 10, 2025
34c215a
Merge branch 'main' into feat/message-content-arrays
evalstate May 11, 2025
41bfd83
Merge remote-tracking branch 'upstream/main' into feat/message-conten…
evalstate May 25, 2025
32fa465
move changes to draft schema
evalstate May 25, 2025
c13b1d1
remove ER
evalstate May 25, 2025
9661bf6
Generate JSON Schema
evalstate May 25, 2025
36634e5
Update changelog
evalstate May 25, 2025
0e7dbe1
update draft docs to reflect changes in schema
evalstate May 25, 2025
4d34819
Merge branch 'feat/message-content-arrays' of https://github.com/eval…
evalstate Jun 4, 2025
d1b2387
Merge remote-tracking branch 'upstream/main' into feat/message-conten…
evalstate Jun 4, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 4 additions & 1 deletion 5 docs/specification/draft/changelog.mdx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ the previous revision, [2025-03-26](/specification/2025-03-26).
## Major changes

1. Removed support for JSON-RPC **[batching](https://www.jsonrpc.org/specification#batch)**
(PR [#416](https://github.com/modelcontextprotocol/specification/pull/416))
(PR [#416](https://github.com/modelcontextprotocol/specification/pull/416))
2. Added support for [structured tool output](https://modelcontextprotocol.io/specification/draft/server/tools#structured-content)
(PR [#371](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/371))
3. Classified MCP servers as [OAuth Resource Servers](https://modelcontextprotocol.io/specification/draft/basic/authorization#2-3-authorization-server-discovery), adding protected resource metadata to discover the corresponding Authorization server. (PR [#338](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/338))
Expand All @@ -18,6 +18,9 @@ the previous revision, [2025-03-26](/specification/2025-03-26).

## Other schema changes

- PromptMessage and SamplingMessage now contain Arrays of content.
Copy link
Member

@dsp-ant dsp-ant Jun 6, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This should be a major change with a note that it's breaking

- TODO

## Full changelog

For a complete list of all changes that have been made since the last protocol revision,
Expand Down
12 changes: 7 additions & 5 deletions 12 docs/specification/draft/client/sampling.mdx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@ Applications **SHOULD**:
- Provide UI that makes it easy and intuitive to review sampling requests
- Allow users to view and edit prompts before sending
- Present generated responses for review before delivery
</Warning>
</Warning>

## Capabilities

Expand Down Expand Up @@ -90,10 +90,12 @@ To request a language model generation, servers send a `sampling/createMessage`
"id": 1,
"result": {
"role": "assistant",
"content": {
"type": "text",
"text": "The capital of France is Paris."
},
"content": [
{
"type": "text",
"text": "The capital of France is Paris."
}
],
"model": "claude-3-sonnet-20240307",
"stopReason": "endTurn"
}
Expand Down
10 changes: 6 additions & 4 deletions 10 docs/specification/draft/server/prompts.mdx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -120,10 +120,12 @@ auto-completed through [the completion API](/specification/draft/server/utilitie
"messages": [
{
"role": "user",
"content": {
"type": "text",
"text": "Please review this Python code:\ndef hello():\n print('world')"
}
"content": [
{
"type": "text",
"text": "Please review this Python code:\ndef hello():\n print('world')"
}
]
}
]
}
Expand Down
83 changes: 46 additions & 37 deletions 83 schema/draft/schema.json
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -468,17 +468,20 @@
"type": "object"
},
"content": {
"anyOf": [
{
"$ref": "#/definitions/TextContent"
},
{
"$ref": "#/definitions/ImageContent"
},
{
"$ref": "#/definitions/AudioContent"
}
]
"items": {
"anyOf": [
{
"$ref": "#/definitions/TextContent"
},
{
"$ref": "#/definitions/ImageContent"
},
{
"$ref": "#/definitions/AudioContent"
}
]
},
"type": "array"
},
"model": {
"description": "The name of the model that generated the message.",
Expand Down Expand Up @@ -1599,20 +1602,23 @@
"description": "Describes a message returned as part of a prompt.\n\nThis is similar to `SamplingMessage`, but also supports the embedding of\nresources from the MCP server.",
"properties": {
"content": {
"anyOf": [
{
"$ref": "#/definitions/TextContent"
},
{
"$ref": "#/definitions/ImageContent"
},
{
"$ref": "#/definitions/AudioContent"
},
{
"$ref": "#/definitions/EmbeddedResource"
}
]
"items": {
"anyOf": [
{
"$ref": "#/definitions/TextContent"
},
{
"$ref": "#/definitions/ImageContent"
},
{
"$ref": "#/definitions/AudioContent"
},
{
"$ref": "#/definitions/EmbeddedResource"
}
]
},
"type": "array"
},
"role": {
"$ref": "#/definitions/Role"
Expand Down Expand Up @@ -1948,17 +1954,20 @@
"description": "Describes a message issued to or received from an LLM API.",
"properties": {
"content": {
"anyOf": [
{
"$ref": "#/definitions/TextContent"
},
{
"$ref": "#/definitions/ImageContent"
},
{
"$ref": "#/definitions/AudioContent"
}
]
"items": {
"anyOf": [
{
"$ref": "#/definitions/TextContent"
},
{
"$ref": "#/definitions/ImageContent"
},
{
"$ref": "#/definitions/AudioContent"
}
]
},
"type": "array"
},
"role": {
"$ref": "#/definitions/Role"
Expand Down Expand Up @@ -2279,7 +2288,7 @@
"type": "string"
},
"outputSchema": {
"description": "An optional JSON Schema object defining the structure of the tool's output returned in \nthe structuredContent field of a CallToolResult.",
"description": "An optional JSON Schema object defining the structure of the tool's output returned in\nthe structuredContent field of a CallToolResult.",
"properties": {
"properties": {
"additionalProperties": {
Expand Down
8 changes: 4 additions & 4 deletions 8 schema/draft/schema.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -646,7 +646,7 @@ export type Role = "user" | "assistant";
*/
export interface PromptMessage {
role: Role;
content: TextContent | ImageContent | AudioContent | EmbeddedResource;
content: (TextContent | ImageContent | AudioContent | EmbeddedResource)[];
}

/**
Expand Down Expand Up @@ -705,7 +705,7 @@ export interface CallToolResult extends Result {
* Whether the tool call ended in an error.
*
* If not set, this is assumed to be false (the call was successful).
*
*
* Any errors that originate from the tool SHOULD be reported inside the result
* object, with `isError` set to true, _not_ as an MCP protocol-level error
* response. Otherwise, the LLM would not be able to see that an error occurred
Expand Down Expand Up @@ -816,7 +816,7 @@ export interface Tool {
};

/**
* An optional JSON Schema object defining the structure of the tool's output returned in
* An optional JSON Schema object defining the structure of the tool's output returned in
* the structuredContent field of a CallToolResult.
*/
outputSchema?: {
Expand Down Expand Up @@ -937,7 +937,7 @@ export interface CreateMessageResult extends Result, SamplingMessage {
*/
export interface SamplingMessage {
role: Role;
content: TextContent | ImageContent | AudioContent;
content: (TextContent | ImageContent | AudioContent)[];
Copy link
Member

@cliffhall cliffhall Jun 2, 2025 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

One last-ditch ask for a backward compatible way to handle this. Defining an ArrayContent type which can contain any of the existing types, and then this could become:

Suggested change
content: (TextContent | ImageContent | AudioContent)[];
content: (TextContent | ImageContent | AudioContent | ArrayContent);

Not certain if there's a reason why it wouldn't work, but thought I'd put it out there.

Copy link
Member Author

@evalstate evalstate Jun 2, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I understand the concern, however the original proposal is still my preference. My reasoning is:

  • Changing content to an Array makes it the same as content in CallToolResult.
  • SDK compatibility for both Client and Server is quite straightforward. E.g. converting from content to [content] or from [content,content] to [Message,Message]. This should mean the rollout at both the SDK and protocol level can be managed. There is example code in fast-agent that does this conversion (as it uses this type internally).
  • It is more directly expressive. For example mcp-webcam development version has image prompts for ICL. These have to be [Message TextContent],[Message ImageContent] rather than the actual LLM API Shape of Message [TextContent,ImageContent].
  • Adoption of Sampling and Prompts containing embedded content is still relatively small in comparison to the broader MCP system, so this will be nowhere near as impactful as a breaking change on CallToolResult.

So the trade-off is between a new type introduced for backwards compatibility, or expressing the Message content semantically. I think because it can be mitigated at the SDK with low effort I fall towards the latter.

}

/**
Expand Down
Morty Proxy This is a proxified and sanitized view of the page, visit original site.