fix(tasks): #626 model task capabilities correctly by alexhancock · Pull Request #627 · modelcontextprotocol/rust-sdk

alexhancock · 2026-01-23T16:45:36Z

Capabilities for tasks take the following form.

Client

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"sampling": {
"createMessage": {}
},
"elicitation": {
"create": {}
}
}
}
}
}

Server

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"tools": {
"call": {}
}
}
}
}
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

jamadeo

Nice! Works on my test with goose.

jamadeo · 2026-01-23T17:18:39Z

+
+ // Verify serialization matches expected format
+ let json = serde_json::to_value(&tasks).unwrap();
+ assert_eq!(json["list"], serde_json::json!({}));


are these really testing all that much?

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.

modelcontextprotocol#627)

alexhancock · 2026-01-23T16:45:36Z

Fixes#626

Capabilities for tasks take the following form.

Client

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"sampling": {
"createMessage": {}
},
"elicitation": {
"create": {}
}
}
}
}
}

Server

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"tools": {
"call": {}
}
}
}
}
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

jamadeo

Nice! Works on my test with goose.

jamadeo · 2026-01-23T17:18:39Z

+
+ // Verify serialization matches expected format
+ let json = serde_json::to_value(&tasks).unwrap();
+ assert_eq!(json["list"], serde_json::json!({}));


are these really testing all that much?

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.

modelcontextprotocol#627)

alexhancock · 2026-01-23T16:45:36Z

Fixes#626

Capabilities for tasks take the following form.

Client

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"sampling": {
"createMessage": {}
},
"elicitation": {
"create": {}
}
}
}
}
}

Server

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"tools": {
"call": {}
}
}
}
}
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

jamadeo

Nice! Works on my test with goose.

jamadeo · 2026-01-23T17:18:39Z

+
+ // Verify serialization matches expected format
+ let json = serde_json::to_value(&tasks).unwrap();
+ assert_eq!(json["list"], serde_json::json!({}));


are these really testing all that much?

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.

modelcontextprotocol#627)

alexhancock · 2026-01-23T16:45:36Z

Fixes#626

Capabilities for tasks take the following form.

Client

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"sampling": {
"createMessage": {}
},
"elicitation": {
"create": {}
}
}
}
}
}

Server

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"tools": {
"call": {}
}
}
}
}
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

jamadeo

Nice! Works on my test with goose.

jamadeo · 2026-01-23T17:18:39Z

+
+ // Verify serialization matches expected format
+ let json = serde_json::to_value(&tasks).unwrap();
+ assert_eq!(json["list"], serde_json::json!({}));


are these really testing all that much?

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.

modelcontextprotocol#627)

alexhancock · 2026-01-23T16:45:36Z

Fixes#626

Capabilities for tasks take the following form.

Client

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"sampling": {
"createMessage": {}
},
"elicitation": {
"create": {}
}
}
}
}
}

Server

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"tools": {
"call": {}
}
}
}
}
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

jamadeo

Nice! Works on my test with goose.

jamadeo · 2026-01-23T17:18:39Z

+
+ // Verify serialization matches expected format
+ let json = serde_json::to_value(&tasks).unwrap();
+ assert_eq!(json["list"], serde_json::json!({}));


are these really testing all that much?

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.

modelcontextprotocol#627)

alexhancock · 2026-01-23T16:45:36Z

Fixes#626

Capabilities for tasks take the following form.

Client

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"sampling": {
"createMessage": {}
},
"elicitation": {
"create": {}
}
}
}
}
}

Server

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"tools": {
"call": {}
}
}
}
}
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

jamadeo

Nice! Works on my test with goose.

jamadeo · 2026-01-23T17:18:39Z

+
+ // Verify serialization matches expected format
+ let json = serde_json::to_value(&tasks).unwrap();
+ assert_eq!(json["list"], serde_json::json!({}));


are these really testing all that much?

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.

modelcontextprotocol#627)

alexhancock · 2026-01-23T16:45:36Z

Fixes#626

Capabilities for tasks take the following form.

Client

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"sampling": {
"createMessage": {}
},
"elicitation": {
"create": {}
}
}
}
}
}

Server

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"tools": {
"call": {}
}
}
}
}
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

jamadeo

Nice! Works on my test with goose.

jamadeo · 2026-01-23T17:18:39Z

+
+ // Verify serialization matches expected format
+ let json = serde_json::to_value(&tasks).unwrap();
+ assert_eq!(json["list"], serde_json::json!({}));


are these really testing all that much?

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.

modelcontextprotocol#627)

alexhancock · 2026-01-23T16:45:36Z

Fixes#626

Capabilities for tasks take the following form.

Client

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"sampling": {
"createMessage": {}
},
"elicitation": {
"create": {}
}
}
}
}
}

Server

{
"capabilities": {
"tasks": {
"list": {},
"cancel": {},
"requests": {
"tools": {
"call": {}
}
}
}
}
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

jamadeo

Nice! Works on my test with goose.

jamadeo · 2026-01-23T17:18:39Z

+
+ // Verify serialization matches expected format
+ let json = serde_json::to_value(&tasks).unwrap();
+ assert_eq!(json["list"], serde_json::json!({}));


are these really testing all that much?

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.

modelcontextprotocol#627)

alexhancock requested review from jamadeo and jokemanfire January 23, 2026 16:45

github-actionsBot added T-test Testing related changes T-config Configuration file changes T-core Core library changes T-model Model/data structure changes labels Jan 23, 2026

alexhancock force-pushed the alexhancock/task-capabilities-format branch from 40145f3 to 38aaf98Compare January 23, 2026 17:18

github-actionsBot added the T-documentation Documentation improvements label Jan 23, 2026

fix(tasks):#626model task capabilities correctly
e20f6df

alexhancock force-pushed the alexhancock/task-capabilities-format branch from 38aaf98 to e20f6dfCompare January 23, 2026 17:20

github-actionsBot removed the T-documentation Documentation improvements label Jan 23, 2026

jamadeo approved these changes Jan 23, 2026
View reviewed changes

alexhancock merged commit 613eafb into mainJan 23, 2026
11 checks passed

github-actionsBot mentioned this pull request Jan 21, 2026
chore: release v0.14.0 #623
Merged

takumi-earth pushed a commit to earthlings-dev/rmcp that referenced this pull request Jan 27, 2026
fix(tasks):modelcontextprotocol#626model task capabilities correctly (
9bcdf59
modelcontextprotocol#627)