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Tag MCP tools for tool-rule matching - #48
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McpServerTool now reports tags identifying its server family, server id and remote tool name, so host tool rules can target a server's tools by the names the server itself uses rather than the slugged registered name. The tinytools dependency is bumped to the revision that provides the tags hook. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
Add a test asserting that tools are tagged with their server and remote name, and that a tag-matching deny rule blocks the call. The tinytools dependency is bumped to 0.5.0, which provides the tag-based rule matching this test exercises. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
The test now borrows the tool value instead of calling as_ref on it, matching the expected argument type and keeping the assertion unchanged. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
Explain that each tool's family is its server label and that tags carry the server label, server id and remote tool name, so host rules can target a server's tools by the names it uses. Note that the registered name's slug and digest suffix cannot be split reliably by a pattern, and that per-server allowed and disallowed lists remain exact fetch-time filters. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
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📝 WalkthroughWalkthroughMCP server tools now expose tags for the server family, server ID, and remote tool name. A test verifies the tags and confirms that a matching ChangesMCP tool identity tags
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✅ Passed checks (4 passed)
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A rabbit tags tools as they hop through the grove Comment |
Update the pinned tinytools git revision to bd60b9b52f1998b4483b9cf107a72d3338e672f8 in both the manifest and the lockfile. The pin is kept in step with the revision tinyagents vendors so the tool types stay unified. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
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Review comments at @crates/tinymcp/src/tools/tool.rs:
- Around line 144-153: Update McpServerTool to retain the original server label
separately from its sanitized family, and have tags() use the original label for
the mcp.server tag. Keep the sanitized family unchanged for model-facing data.
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The mcp.server tag was built from the sanitized family, so a host rule written against the configured server label could stop matching once the label was truncated or stripped for the model. The tool now retains the raw configured label and uses it for the tag, while the model-facing family stays sanitized. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
Co-authored-by: Medulla <medulla@tinyhumans.ai>
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Tool calls with no arguments now deserialize into an empty map instead of failing, so bridged tools that take no parameters can be invoked. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
Add a test asserting that the generic dispatcher reports the per-server tool target, so a tool rule written for that tool also binds mcp_call_tool. The bridge source change is only a rustfmt reflow of the indirect_target body. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
The test referenced the disambiguated tool name through an extra `super::` hop, which no longer resolves after the module layout settled. Point it at the correct path so the assertion compiles again. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
The test now calls the naming helper through its public module path instead of the removed re-export, keeping the assertion compiling after the helper moved. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
Tiny Sweeper reviewTiny Sweeper completed its review; deterministic results follow. State: Changes requested Review snapshot
Completeness: Complete What changedNo supported behavioral explanation was produced. Features
TestsNo supported feature-to-test mapping was produced. Test execution is not inferred. Findings
Resolved this pass
Before merge
How this fits togetherflowchart LR
n0["McpServerTool<br/>changed"]:::changed
n1["tools_for"]:::impacted
n2["execute_with_options"]:::impacted
n3["McpToolInvoker"]:::impacted
n4["Result"]:::impacted
n5["execute"]:::impacted
n6["...server_caches_its_listing_and_is_callable"]:::impacted
n0 -->|uses| n3
n1 -->|uses| n0
n1 -->|uses| n3
n2 -->|uses| n4
n5 -->|calls| n2
n5 -->|uses| n4
n6 -->|calls| n1
n6 -->|tests| n1
classDef changed fill:#0d4429,stroke:#238636,color:#e6edf3
classDef impacted fill:#161b22,stroke:#6e7681,color:#c9d1d9
classDef flagged fill:#5a1e02,stroke:#d93f0b,color:#ffffff
classDef blocking fill:#67060c,stroke:#f85149,color:#ffffff
Agent review detailscritique
security
tests
commits
description
e2e
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Requesting changes: 1 lane(s) blocking, worst finding is high.
Fix or reply to the findings below and push. The next review clears this automatically once they are gone — you should not need to dismiss anything by hand.
$0.0223 · 308,616 in / 18,599 out · 37,530 cached (12%) · gpt-5.6-luna, glm-5.3-flash
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security: $0.0107 · 132,228 in / 5,249 out · 12,661 cached (10%) · gpt-5.6-luna
tests: $0.0002 · 16,329 in / 2,142 out · 3,712 cached (23%) · glm-5.3-flash
description: $0.0001 · 6,687 in / 502 out · 1,536 cached (23%) · glm-5.3-flash
The indirect target for the MCP call tool now resolves server and tool through the same argument normalization used at dispatch, so tool rules judge the identifier that will actually run rather than the raw string. A test covers a fenced, padded identifier being normalized consistently. Auto-committed-on: dragonfly Co-authored-by: Medulla <medulla@tinyhumans.ai>
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Requesting changes: 3 lane(s) blocking, worst finding is high.
Fix or reply to the findings below and push. The next review clears this automatically once they are gone — you should not need to dismiss anything by hand.
$0.0066 · 108,328 in / 17,033 out · 13,242 cached (12%) · gpt-5.6-luna, glm-5.3-flash
critique: $0.0016 · 26,227 in / 3,565 out · 2,626 cached (10%) · gpt-5.6-luna, glm-5.3-flash
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tests: $0.0003 · 28,525 in / 5,529 out · 3,136 cached (11%) · glm-5.3-flash
description: $0.0001 · 7,108 in / 218 out · 0 cached (0%) · glm-5.3-flash
| target.category = Some(tinytools::ToolCategory::Workflow); | ||
| let call = tinytools::IndirectCall::new(target); | ||
| Some( | ||
| match args |
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Do not discard invalid arguments before evaluating rules
When arguments is a non-object value or an invalid JSON string, normalize_tool_arguments returns an error and this and_then(...ok()) converts it to None, producing an indirect call with no arguments. Argument-based deny rules therefore do not see the supplied payload and can allow the outer mcp_call_tool call, even though dispatch will later reject the same malformed payload. Preserve the normalization error through rule evaluation, or represent the original arguments in the indirect target so policy cannot be bypassed by malformed input.
Additional security observation
Do not discard invalid arguments before evaluating rules
[RULE] authorization-bypass
When argument normalization fails, this silently omits the indirect call arguments instead of preserving the invalid input or rejecting the call. Argument-based tool rules therefore evaluate against a call with no arguments, so a deny rule that should apply to the supplied payload is not evaluated consistently with the request that will be dispatched. Preserve the original arguments for policy evaluation, or make target construction fail closed whenever normalization fails.
[RULE] discarded-errors ·
| let tool = required_string_arg(args, "tool").ok()?; | ||
| let (server, tool) = (server.as_str(), tool.as_str()); | ||
| let mut target = | ||
| tinytools::ToolSubject::named(disambiguated_tool_name(server, server, tool)) |
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Build the indirect target from the real server id, not the label
indirect_target passes the server argument (the configured label) as both the id and the label to disambiguated_tool_name(server, server, tool), and tags it mcp.server_id:{server}. The registered per-server tools are named with the server's actual id (disambiguated_tool_name(server_id, server_label, tool) in naming.rs), and their mcp.server_id: tag carries that id. So whenever server_id != label, the digest differs — the indirect subject's name will not equal the registered tool's name — and a host rule targeting mcp.server_id:<real id> matches the direct route but not mcp_call_tool. That defeats the function's stated purpose ("bind the operation whichever route the model takes") and is a policy gap on the dispatcher path. The test masks this because its fixture's server id equals its label, and the name assertion calls the same function with the same arguments, so it cannot fail on this. Resolve the server record from self.registry and use its server_id for the digest and the mcp.server_id: tag.
[RULE] subject-identity-mismatch ·
1 participant
Summary
Tags every
McpServerTool(thetoolsfeature) withmcp.server:<label>,mcp.server_id:<id>andmcp.tool:<remote name>. This lets a host'stinytools::ToolRules(tinyhumansai/tinytools#57) target one server's tools by the names the server itself uses, for example{ "effect": "deny", "match": { "tags": "mcp.tool:delete*" } }.The registered name,
mcp_<server>_<tool>_<hash>, is a slug with a digest suffix, so a name glob cannot reliably split it.The per-server
allowed_tools/disallowed_toolslists are unchanged: they stay exact, fetch-time filters inside the registry. Glob rules apply on the host, through the harness gate (tinyhumansai/tinyagents#353).Dependency
Tool::tagslanded in tinyhumansai/tinytools#57. The workspacetinytoolsrev is pinned to its merge commit,bd60b9b.API or behavior changes
McpServerTool::tags()returns the three tags. This is additive.tinytoolsrev moves to the tinytools#57 merge commit.toolsfeature is linked by the host only.Validation
cargo +1.98.0 clippy --all-targets --all-features -- -D warningspasses. Stable 1.96 does not knowclippy::unused_async_trait_impl, which is already used on main.cargo test --all-featurespasses with 0 failures.tools::test::a_tool_is_tagged_so_rules_can_target_its_server_and_remote_name, which asserts the tags and a deny rule overmcp.tool:delete*.Summary by CodeRabbit