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Merged
DaleSeo merged 7 commits into from
Dec 17, 2025
Merged

Add outputSchema support #509

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438eae6
feat: add outputSchema support
DaleSeo Nov 28, 2025
743112c
chore: add changeset
DaleSeo Dec 1, 2025
013c73e
fix: include output_schema in tool character count
DaleSeo Dec 2, 2025
e3c6725
refactor: reduce enum description verbosity
DaleSeo Dec 16, 2025
0641b2a
feat: make output schema generation opt-in
DaleSeo Dec 16, 2025
9ae2b98
docs: add enable_output_schema config option
DaleSeo Dec 16, 2025
ad78379
chore: update changeset
DaleSeo Dec 16, 2025
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10 changes: 10 additions & 0 deletions .changesets/feat_output_schema.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
### Add outputSchema support - @DaleSeo PR #509

This PR implements support for the MCP specification's [outputSchema](https://modelcontextprotocol.io/specification/2025-11-25/server/tools#output-schema) field on tools, which allows tools to declare the expected structure of their output. This helps LLMs better understand and reason about GraphQL response data.
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@andrewmcgivery andrewmcgivery Dec 16, 2025

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Can we please include the part about needing to opt into it and include a config example? :)

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@DaleSeo DaleSeo Dec 16, 2025

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Good call! Updated the changeset.


This feature is opt-in to avoid additional token overhead. To enable it, add the following to your config:

```yaml
overrides:
enable_output_schema: true
```
9 changes: 9 additions & 0 deletions crates/apollo-mcp-server/src/apps.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,7 @@ pub(crate) fn load_from_path(
mutation_mode: MutationMode,
disable_type_description: bool,
disable_schema_description: bool,
enable_output_schema: bool,
) -> Result<Vec<App>, String> {
let Ok(apps_dir) = path.read_dir() else {
return Ok(Vec::new());
Expand Down Expand Up @@ -146,6 +147,7 @@ pub(crate) fn load_from_path(
mutation_mode,
disable_type_description,
disable_schema_description,
enable_output_schema,
) {
Err(err) => {
return Err(format!(
Expand Down Expand Up @@ -393,6 +395,7 @@ mod test_load_from_path {
MutationMode::All,
false,
false,
true,
)
.expect("Failed to load apps");
assert_eq!(apps.len(), 1);
Expand Down Expand Up @@ -428,6 +431,7 @@ mod test_load_from_path {
MutationMode::All,
false,
false,
true,
)
.expect("Failed to load apps");
assert_eq!(apps.len(), 1);
Expand Down Expand Up @@ -477,6 +481,7 @@ mod test_load_from_path {
MutationMode::All,
false,
false,
true,
)
.expect("Failed to load apps");
assert_eq!(apps.len(), 1);
Expand Down Expand Up @@ -536,6 +541,7 @@ mod test_load_from_path {
MutationMode::All,
false,
false,
true,
)
.expect("Failed to load apps");
assert_eq!(apps.len(), 1);
Expand Down Expand Up @@ -592,6 +598,7 @@ mod test_load_from_path {
MutationMode::All,
false,
false,
true,
)
.expect("Failed to load apps");

Expand Down Expand Up @@ -655,6 +662,7 @@ mod test_load_from_path {
MutationMode::All,
false,
false,
true,
);

assert!(apps.is_err());
Expand Down Expand Up @@ -701,6 +709,7 @@ mod test_load_from_path {
MutationMode::All,
false,
false,
true,
);

assert!(apps.is_err());
Expand Down
12 changes: 6 additions & 6 deletions crates/apollo-mcp-server/src/apps/execution.rs
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Expand Up @@ -163,7 +163,7 @@ mod tests {
"query Primary($apples: Int) { apples(first: $apples) }".to_string(),
None,
))
.into_operation(&schema, None, MutationMode::All, true, true)
.into_operation(&schema, None, MutationMode::All, true, true, true)
.unwrap()
.unwrap(),
);
Expand All @@ -174,7 +174,7 @@ mod tests {
"query FirstPrefetch($bananas: Int) { bananas(first: $bananas) }".to_string(),
None,
))
.into_operation(&schema, None, MutationMode::All, true, true)
.into_operation(&schema, None, MutationMode::All, true, true, true)
.unwrap()
.unwrap(),
);
Expand All @@ -183,7 +183,7 @@ mod tests {
"query SecondPrefetch($oranges: Int) { oranges(first: $oranges) }".to_string(),
None,
))
.into_operation(&schema, None, MutationMode::All, true, true)
.into_operation(&schema, None, MutationMode::All, true, true, true)
.unwrap()
.unwrap(),
);
Expand Down Expand Up @@ -314,7 +314,7 @@ mod tests {
tools: vec![AppTool {
operation: Arc::new(
RawOperation::from(("query GetId { id }".to_string(), None))
.into_operation(&schema, None, MutationMode::All, false, false)
.into_operation(&schema, None, MutationMode::All, false, false, true)
.unwrap()
.unwrap(),
),
Expand Down Expand Up @@ -361,7 +361,7 @@ mod tests {
tools: vec![AppTool {
operation: Arc::new(
RawOperation::from(("query GetId { id }".to_string(), None))
.into_operation(&schema, None, MutationMode::All, false, false)
.into_operation(&schema, None, MutationMode::All, false, false, true)
.unwrap()
.unwrap(),
),
Expand Down Expand Up @@ -400,7 +400,7 @@ mod tests {
tools: vec![AppTool {
operation: Arc::new(
RawOperation::from(("query GetId { id }".to_string(), None))
.into_operation(&schema, None, MutationMode::All, false, false)
.into_operation(&schema, None, MutationMode::All, false, false, true)
.unwrap()
.unwrap(),
),
Expand Down
1 change: 1 addition & 0 deletions crates/apollo-mcp-server/src/main.rs
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Expand Up @@ -128,6 +128,7 @@ async fn main() -> anyhow::Result<()> {
.mutation_mode(config.overrides.mutation_mode)
.disable_type_description(config.overrides.disable_type_description)
.disable_schema_description(config.overrides.disable_schema_description)
.enable_output_schema(config.overrides.enable_output_schema)
.disable_auth_token_passthrough(match transport {
apollo_mcp_server::server::Transport::Stdio => false,
apollo_mcp_server::server::Transport::SSE { auth, .. } => auth
Expand Down
6 changes: 3 additions & 3 deletions crates/apollo-mcp-server/src/operations/execution.rs
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Expand Up @@ -54,7 +54,7 @@ mod tests {
.validate()
.unwrap();
let operation = RawOperation::from(("query GetHello { hello }".to_string(), None))
.into_operation(&schema, None, MutationMode::All, true, true)
.into_operation(&schema, None, MutationMode::All, true, true, true)
.unwrap()
.unwrap();

Expand All @@ -78,11 +78,11 @@ mod tests {
.unwrap();
let operations = [
RawOperation::from(("query GetHello { hello }".to_string(), None))
.into_operation(&schema, None, MutationMode::All, true, true)
.into_operation(&schema, None, MutationMode::All, true, true, true)
.unwrap()
.unwrap(),
RawOperation::from(("query GetWorld { hello }".to_string(), None))
.into_operation(&schema, None, MutationMode::All, true, true)
.into_operation(&schema, None, MutationMode::All, true, true, true)
.unwrap()
.unwrap(),
];
Expand Down
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