Tools Reference

Parameters and defaults for the eight MCP tools the Fuse server exposes to AI clients.

The Fuse MCP server exposes eight tools an AI client can call to request scoped, reduced codebase context. MCP (Model Context Protocol) is the open protocol that lets an AI client call external tools. This page documents each tool and its parameters so that an agent or its author can choose the right call and supply correct arguments.

This page is for engineers writing agent instructions and for experts who need the exact default of each parameter.

Purpose and Scope

Every tool here is read-only and runs its fusion in memory, returning the result in the tool response rather than writing a file. Each tool maps to an equivalent CLI invocation; the flag forms are documented in Options Reference. For the recommended order in which to call these tools, see Recommended Workflows. For passive reads through URIs, see Resources Reference.

The three scoping parameters (focus, changedSince, and query) are mutually exclusive. A single fusion uses at most one of them.

The scoping tools share one retrieval engine, documented in Scoping Internals. Three behaviors are worth knowing when calling them. Focus pulls in both the files a seed depends on and the files that depend on it (its dependents), so a seed reaches its callers as well as its callees. Search ranks with BM25F, weighting a file's declared type and member names and its path above its body, so the file that declares a concept ranks above files that merely mention it. When maxTokens is set, the result is emitted most-relevant first, so the files closest to the seed survive the limit.

fuse_toc

Table of contents (directory tree, symbol outline, per-file token costs) instead of file bodies. The cheapest first call: survey the codebase, then fetch specific files.

Parameter	Type	Default	Meaning
`path`	string	required	Source directory to fuse
`excludeDirectories`	string[]	null	Directory names to skip
`excludeFiles`	string[]	null	File names to exclude
`excludePatterns`	string[]	null	Glob patterns to exclude
`excludeTestProjects`	bool	false	Skip all test project directories

fuse_ask

Give a task and a token budget; Fuse picks the scoping strategy and packs the context to the budget. One call instead of survey-then-scope. The strategy is chosen from the task text: a broad question maps to a skeleton, a task naming one type maps to focus on that type, and anything else maps to search. Focus falls back to search when the named type does not resolve.

Parameter	Type	Default	Meaning
`path`	string	required	Source directory to fuse
`task`	string	required	What you need to do or find, in natural language
`tokenBudget`	int	20000	Maximum tokens the returned context may use
`excludeDirectories`	string[]	null	Directory names to skip
`excludeFiles`	string[]	null	File names to exclude
`excludePatterns`	string[]	null	Glob patterns to exclude
`excludeTestProjects`	bool	false	Skip all test project directories

The result is prefixed with a one-line note naming the chosen strategy.

fuse_skeleton

Structural skeleton only (signatures, no bodies). Cold-start architecture review.

Parameter	Type	Default	Meaning
`path`	string	required	Source directory to fuse
`excludeDirectories`	string[]	null	Directory names to skip
`excludeFiles`	string[]	null	File names to exclude
`excludePatterns`	string[]	null	Glob patterns to exclude
`excludeTestProjects`	bool	false	Skip all test project directories
`semanticMarkers`	bool	false	Prepend structural annotation comments
`publicApi`	bool	false	Keep only public and protected member skeletons
`maxTokens`	int	null	Hard token limit, or unlimited
`trackTopTokenFiles`	bool	false	Append the top token-consuming files to the stats comment

This tool always emits a skeleton (signatures, no bodies). Set publicApi to true to narrow the skeleton to public and protected members only.

fuse_focus

Scope to a type, file, or path plus dependency traversal.

Parameter	Type	Default	Meaning
`path`	string	required	Source directory to fuse
`focus`	string	required	Type name, filename, or path used as the seed
`depth`	int	1	Dependency hops to traverse out from the seed
`excludeDirectories`	string[]	null	Directory names to skip
`excludeFiles`	string[]	null	File names to exclude
`excludePatterns`	string[]	null	Glob patterns to exclude
`excludeTestProjects`	bool	false	Skip all test project directories
`level`	none \| standard \| aggressive \| skeleton \| publicApi	none	C# structural reduction level
`maxTokens`	int	null	Hard token limit, or unlimited
`trackTopTokenFiles`	bool	false	Append the top token-consuming files to the stats comment
`session`	string	null	Session id: omit files already returned under this id earlier in the session

A focus of the form Type.Member scopes the seed file to that member when the precision tier is active (the server is started with FUSE_SEMANTIC).

fuse_search

BM25F query-scoped fusion plus dependency expansion.

Parameter	Type	Default	Meaning
`path`	string	required	Source directory to fuse
`query`	string	required	Natural-language or keyword query, ranked with BM25F
`queryTop`	int	10	Number of top-ranked files used to seed dependency expansion
`depth`	int	1	Dependency hops to traverse out from the seed files
`rerank`	bool	false	Rerank the BM25 candidates with embedding-vector similarity (hybrid retrieval)
`excludeDirectories`	string[]	null	Directory names to skip
`excludeFiles`	string[]	null	File names to exclude
`excludePatterns`	string[]	null	Glob patterns to exclude
`excludeTestProjects`	bool	false	Skip all test project directories
`level`	none \| standard \| aggressive \| skeleton \| publicApi	none	C# structural reduction level
`maxTokens`	int	null	Hard token limit, or unlimited
`trackTopTokenFiles`	bool	false	Append the top token-consuming files to the stats comment
`session`	string	null	Session id: omit files already returned under this id earlier in the session

fuse_changes

Files changed since a git ref plus optional dependents.

Parameter	Type	Default	Meaning
`path`	string	required	Source directory to fuse
`changedSince`	string	required	Git ref (branch, commit, or HEAD~N) to diff against
`includeDependents`	bool	true	Also include first-degree dependents of the changed files
`review`	bool	false	Prepend a review map: diff hunks and direct callers for each changed file
`excludeDirectories`	string[]	null	Directory names to skip
`excludeFiles`	string[]	null	File names to exclude
`excludePatterns`	string[]	null	Glob patterns to exclude
`excludeTestProjects`	bool	false	Skip all test project directories
`level`	none \| standard \| aggressive \| skeleton \| publicApi	none	C# structural reduction level
`maxTokens`	int	null	Hard token limit, or unlimited
`trackTopTokenFiles`	bool	false	Append the top token-consuming files to the stats comment

fuse_dotnet

Full-control .NET fusion with all options.

Parameter	Type	Default	Meaning
`path`	string	required	Source directory to fuse
`excludeDirectories`	string[]	null	Directory names to skip
`excludeFiles`	string[]	null	File names to exclude
`excludePatterns`	string[]	null	Glob patterns to exclude
`includeExtensions`	string[]	null	Extensions to add on top of the DotNet template defaults
`excludeExtensions`	string[]	null	Extensions to remove from the DotNet template defaults
`onlyExtensions`	string[]	null	Extensions to use exclusively, ignoring template defaults
`maxFileSizeKb`	int	0	Maximum file size in KB; 0 means unlimited
`excludeTestProjects`	bool	false	Skip all test project directories
`excludeUnitTestProjects`	bool	false	Skip only unit test project directories
`level`	none \| standard \| aggressive \| skeleton \| publicApi	none	C# structural reduction level
`semanticMarkers`	bool	false	Prepend structural annotation comments
`focus`	string	null	Type name, filename, or path to scope around
`depth`	int	1	Dependency traversal depth for focus and query scoping
`changedSince`	string	null	Git ref to scope to changed files
`includeDependents`	bool	true	Include first-degree dependents of changed files
`query`	string	null	BM25 query to scope fusion
`queryTop`	int	10	Number of top-ranked seed files for query scoping
`patternSummary`	bool	false	Detect and append a cross-codebase pattern summary
`collapseGenerated`	bool	false	Collapse EF Core migration and model-snapshot bodies to signatures
`maxTokens`	int	null	Hard token limit, or unlimited
`trackTopTokenFiles`	bool	false	Append the top token-consuming files to the stats comment
`gitStats`	bool	false	Include git churn stats in the manifest

fuse_generic

Generic fusion for any template (Python, Go, Rust, and others).

Parameter	Type	Default	Meaning
`path`	string	required	Source directory to fuse
`template`	string	null	Template name; null infers the template from the directory
`excludeDirectories`	string[]	null	Directory names to skip
`excludeFiles`	string[]	null	File names to exclude
`excludePatterns`	string[]	null	Glob patterns to exclude
`includeExtensions`	string[]	null	Extensions to add on top of the template defaults
`excludeExtensions`	string[]	null	Extensions to remove from the template defaults
`onlyExtensions`	string[]	null	Extensions to use exclusively, ignoring template defaults
`maxFileSizeKb`	int	0	Maximum file size in KB; 0 means unlimited
`excludeTestProjects`	bool	false	Skip all test project directories
`changedSince`	string	null	Git ref to scope to changed files
`includeDependents`	bool	true	Include first-degree dependents of changed files
`maxTokens`	int	null	Hard token limit, or unlimited
`trackTopTokenFiles`	bool	false	Append the top token-consuming files to the stats comment
`gitStats`	bool	false	Include git churn stats in the manifest

What This Does Not Cover

This page documents tool parameters and defaults. It does not cover the resource URIs, the call sequence, or the output structure. See Resources Reference for URI reads, Recommended Workflows for the call order, and Output Specification for the response format. The CLI flag equivalent of each parameter is in Options Reference.

Continue to Resources Reference for the passive URI reads, or to Options Reference for the matching command-line flags.