') + ')', 'gi'); if (regex.test(text)) { found = true; var frag = document.createDocumentFragment(); var parts = text.split(regex); parts.forEach(function(part, i) { if (i % 2 === 0) { frag.appendChild(document.createTextNode(part)); } else { var span = document.createElement('span'); span.className = 'userscript-highlight'; span.textContent = part; frag.appendChild(span); } }); node.parentNode.replaceChild(frag, node); } }); } else if (node.nodeType === 1 && node.childNodes) { // element var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT']; if (!skipTags.includes(node.tagName)) { Array.from(node.childNodes).forEach(highlight); } } } highlight(document.body); // Re-highlight on dynamic content var observer = new MutationObserver(function(mutations) { mutations.forEach(function(m) { m.addedNodes.forEach(function(node) { if (node.nodeType === 1 || node.nodeType === 3) highlight(node); }); }); }); observer.observe(document.body, { childList: true, subtree: true }); })(); } } catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + ', 'i'); if (__m === '*' || __re.test(location.href)) { // Strip utm_, fbclid, gclid, etc. from all links on page (function() { var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content', 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid', 'ref', 'ref_src', 'source', 'medium', 'campaign']; function cleanUrl(url) { try { var u = new URL(url, window.location.origin); var changed = false; trackingParams.forEach(function(p) { if (u.searchParams.has(p)) { u.searchParams.delete(p); changed = true; } }); return changed ? u.toString() : url; } catch (e) { return url; } } function cleanLinks() { document.querySelectorAll('a[href]').forEach(function(a) { var clean = cleanUrl(a.href); if (clean !== a.href) a.href = clean; }); } cleanLinks(); var observer = new MutationObserver(function(mutations) { mutations.forEach(function(m) { m.addedNodes.forEach(function(node) { if (node.nodeType === 1) { if (node.tagName === 'A') cleanLinks(); node.querySelectorAll('a[href]').forEach(function(a) { var clean = cleanUrl(a.href); if (clean !== a.href) a.href = clean; }); } }); }); }); observer.observe(document.body, { childList: true, subtree: true }); })(); } } catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); } })(); (function(){ try { var __m = "youtube.com"; var __re = new RegExp('^' + "youtube\\.com" + ', 'i'); if (__m === '*' || __re.test(location.href)) { // Auto-enable theater mode on YouTube (function() { function tryTheater() { var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]'); if (btn && !btn.classList.contains('activated')) { btn.click(); } } // Try immediately tryTheater(); // Try after navigation (SPA) var lastUrl = location.href; setInterval(function() { if (location.href !== lastUrl) { lastUrl = location.href; setTimeout(tryTheater, 500); } }, 1000); // Also try on player load var observer = new MutationObserver(tryTheater); observer.observe(document.body, { childList: true, subtree: true }); })(); } } catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + ', 'i'); if (__m === '*' || __re.test(location.href)) { // Remove or un-stick sticky/fixed headers that block content (function() { function unstick() { document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) { if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') { el.style.position = 'static'; el.style.top = 'auto'; el.style.zIndex = 'auto'; } }); } unstick(); var observer = new MutationObserver(unstick); observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] }); })(); } } catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); } })(); })(); feat!: relax tool result structuredContent type (SEP-2106) by DaleSeo · Pull Request #919 · modelcontextprotocol/rust-sdk · GitHub
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feat!: relax tool result structuredContent type (SEP-2106) - #919

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alexhancock merged 1 commit into
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fix/tool-result-content-structured-value
Jun 26, 2026
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feat!: relax tool result structuredContent type (SEP-2106)#919
alexhancock merged 1 commit into
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fix/tool-result-content-structured-value

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@DaleSeo

@DaleSeoDaleSeo commented Jun 23, 2026•
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Motivation and Context

This was discovered while reviewing PR #895. Besides CallToolResult, ToolResultContent should also be typed with its structured content as Option<Value> to accommodate any JSON value.

2025-11-252026-07-28
2026-06-23 at 15 42 592026-06-23 at 15 41 47

How Has This Been Tested?

Added tests

Breaking Changes

Yes. The public field ToolResultContent.structured_content changes type from Option<JsonObject> to Option<Value>.

The green SemVer Check is a false negative due to known upstream gap: obi1kenobi/cargo-semver-checks#148

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Documentation update

Checklist

  • I have read the MCP Documentation
  • My code follows the repository's style guidelines
  • New and existing tests pass locally
  • I have added appropriate error handling
  • I have added or updated documentation as needed

@github-actionsgithub-actionsBot added T-test Testing related changes T-config Configuration file changes T-core Core library changes labels Jun 23, 2026
@DaleSeoDaleSeo self-assigned this Jun 23, 2026
@github-actionsgithub-actionsBot added the T-model Model/data structure changes label Jun 23, 2026
@DaleSeo
DaleSeo marked this pull request as ready for review June 23, 2026 19:56
@DaleSeo
DaleSeo requested a review from a team as a code ownerJune 23, 2026 19:56
@DaleSeoDaleSeo changed the title feat!: relax tool result structuredContent typefeat!: relax tool result structuredContent type (SEP-2106)Jun 23, 2026
@DaleSeo
DaleSeoforce-pushed the fix/tool-result-content-structured-value branch from 97d6a3d to 4dcb918CompareJune 25, 2026 23:26
alexhancock
alexhancock approved these changes Jun 26, 2026
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Comment threadcrates/rmcp/tests/test_sampling.rs

#[tokio::test]
async fn test_tool_result_content_with_primitive_structured_content() -> Result<()> {
let structured = serde_json::json!(42);

@alexhancockalexhancockJun 26, 2026•
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Worth one that loops through all the possible primitive types (string, number, boolean, null) and does the same test? This way it would catch if anyone changes it in some way that drops support for something.

@DaleSeoDaleSeoJun 26, 2026

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Good call, @alexhancock. I've opened #931 to bring in rstest for these repeated rmcp unit-test clusters (it also clears the existing -D warnings clippy failures on the test targets). Once #931 lands I'll come back and parametrize this with rstest so each primitive shows up as its own reported case.

@alexhancock
alexhancock merged commit b8a936c into mainJun 26, 2026
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alexhancock deleted the fix/tool-result-content-structured-value branch June 26, 2026 18:57
@github-actionsgithub-actionsBot mentioned this pull request Jun 26, 2026
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@DaleSeo
DaleSeo restored the fix/tool-result-content-structured-value branch June 26, 2026 19:06
@DaleSeoDaleSeo mentioned this pull request Jun 26, 2026
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DaleSeo added a commit that referenced this pull request Jun 26, 2026
@DaleSeo
Revert "feat!: relax tool result structuredContent type (#919)" (#932)
4b9bea7
This reverts commit b8a936c.
@DaleSeoDaleSeo linked an issue Jun 26, 2026 that may be closed by this pull request
Implement SEP-2106: Tool schemas conform to JSON Schema 2020-12 #874
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DaleSeo added a commit that referenced this pull request Jun 26, 2026
@DaleSeo
feat!: relax tool result structuredContent type (SEP-2106)
5104d3d
Re-applies #919 (reverted by #932): ToolResultContent.structured_content
becomes Option<Value> so non-object structured content is accepted,
matching CallToolResult and SEP-2106.
BREAKING CHANGE: ToolResultContent.structured_content changes from
Option<JsonObject> to Option<Value>.
DaleSeo added a commit that referenced this pull request Jun 26, 2026
@DaleSeo
feat!: relax tool result structuredContent type (SEP-2106)
6755d12
Re-applies #919 (reverted by #932): ToolResultContent.structured_content
becomes Option<Value> so non-object structured content is accepted,
matching CallToolResult and SEP-2106.
BREAKING CHANGE: ToolResultContent.structured_content changes from
Option<JsonObject> to Option<Value>.
DaleSeo added a commit that referenced this pull request Jul 8, 2026
@DaleSeo
feat!: relax tool result structuredContent type (SEP-2106) (#933)
ba00b15
Re-applies #919 (reverted by #932): ToolResultContent.structured_content
becomes Option<Value> so non-object structured content is accepted,
matching CallToolResult and SEP-2106.
BREAKING CHANGE: ToolResultContent.structured_content changes from
Option<JsonObject> to Option<Value>.
@DaleSeoDaleSeo modified the milestone: 2026-07-28 specJul 13, 2026
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Implement SEP-2106: Tool schemas conform to JSON Schema 2020-12

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