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feat: add --tools flag to filter exposed MCP tools (#167)

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Adds `-O`/`-tools` CLI flag and `GITEA_TOOLS` environment variable
accepting a comma-separated list of tool names. When set, only the
listed tools are exposed to MCP clients, which lets AI agents trim
their tool context. Composes with `--read-only`. Unknown names are
logged at startup so typos surface instead of failing silently.

Co-Authored-By: silverwind <me@silverwind.io>
Co-Authored-By: Claude (Opus 4.7) <noreply@anthropic.com>
This commit is contained in:
Martin Mikula
2026-05-10 12:07:16 +02:00
committed by silverwind
parent cd82f6f207
commit bcefbaa9c1
5 changed files with 181 additions and 50 deletions
Download Patch File Download Diff File Expand all files Collapse all files
cmd/cmd.go
+16
View File
@@ -17,6 +17,7 @@ var (
host string
port int
token string
tools string
version bool
)
@@ -31,6 +32,9 @@ func init() {
flag.StringVar(&token, "token", "", "")
flag.BoolVar(&flagPkg.ReadOnly, "r", false, "")
flag.BoolVar(&flagPkg.ReadOnly, "read-only", false, "")
defaultTools := os.Getenv("GITEA_TOOLS")
flag.StringVar(&tools, "O", defaultTools, "")
flag.StringVar(&tools, "tools", defaultTools, "")
flag.BoolVar(&flagPkg.Debug, "d", false, "")
flag.BoolVar(&flagPkg.Debug, "debug", false, "")
flag.BoolVar(&flagPkg.Insecure, "k", false, "")
@@ -48,6 +52,7 @@ func init() {
fmt.Fprintf(w, " -p, -port <number>\tHTTP server port (default: 8080)\n")
fmt.Fprintf(w, " -T, -token <token>\tPersonal access token\n")
fmt.Fprintf(w, " -r, -read-only\tExpose only read-only tools\n")
fmt.Fprintf(w, " -O, -tools <names>\tComma-separated list of tool names to expose\n")
fmt.Fprintf(w, " -d, -debug\tEnable debug mode\n")
fmt.Fprintf(w, " -k, -insecure\tIgnore TLS certificate errors\n")
fmt.Fprintf(w, " -v, -version\tPrint version and exit\n")
@@ -59,6 +64,7 @@ func init() {
fmt.Fprintf(w, " GITEA_HOST\tOverride Gitea host URL\n")
fmt.Fprintf(w, " GITEA_INSECURE\tSet to 'true' to ignore TLS errors\n")
fmt.Fprintf(w, " GITEA_READONLY\tSet to 'true' for read-only mode\n")
fmt.Fprintf(w, " GITEA_TOOLS\tComma-separated list of tool names to expose\n")
fmt.Fprintf(w, " MCP_MODE\tOverride transport mode\n")
w.Flush()
}
@@ -95,6 +101,16 @@ func init() {
flagPkg.ReadOnly = true
}
allowed := map[string]struct{}{}
for t := range strings.SplitSeq(tools, ",") {
if t = strings.TrimSpace(t); t != "" {
allowed[t] = struct{}{}
}
}
if len(allowed) > 0 {
flagPkg.AllowedTools = allowed
}
if os.Getenv("GITEA_DEBUG") == "true" {
flagPkg.Debug = true
}
operation/operation.go
+14 -40
View File
@@ -27,53 +27,27 @@ import (
mcpContext "gitea.com/gitea/gitea-mcp/pkg/context"
"gitea.com/gitea/gitea-mcp/pkg/flag"
"gitea.com/gitea/gitea-mcp/pkg/log"
"gitea.com/gitea/gitea-mcp/pkg/tool"
"github.com/mark3labs/mcp-go/server"
)
var mcpServer *server.MCPServer
var (
mcpServer *server.MCPServer
domainTools = []*tool.Tool{
user.Tool, actions.Tool, repo.Tool, notification.Tool, issue.Tool,
label.Tool, milestone.Tool, packages.Tool, pull.Tool, search.Tool,
version.Tool, wiki.Tool, timetracking.Tool,
}
)
func RegisterTool(s *server.MCPServer) {
// User Tool
s.AddTools(user.Tool.Tools()...)
// Actions Tool
s.AddTools(actions.Tool.Tools()...)
// Repo Tool
s.AddTools(repo.Tool.Tools()...)
// Notification Tool
s.AddTools(notification.Tool.Tools()...)
// Issue Tool
s.AddTools(issue.Tool.Tools()...)
// Label Tool
s.AddTools(label.Tool.Tools()...)
// Milestone Tool
s.AddTools(milestone.Tool.Tools()...)
// Package Tool
s.AddTools(packages.Tool.Tools()...)
// Pull Tool
s.AddTools(pull.Tool.Tools()...)
// Search Tool
s.AddTools(search.Tool.Tools()...)
// Version Tool
s.AddTools(version.Tool.Tools()...)
// Wiki Tool
s.AddTools(wiki.Tool.Tools()...)
// Time Tracking Tool
s.AddTools(timetracking.Tool.Tools()...)
for _, t := range domainTools {
s.AddTools(t.Tools()...)
}
s.DeleteTools("")
tool.WarnUnmatchedAllowedTools(domainTools...)
}
// parseAuthToken extracts the token from an Authorization header.
pkg/flag/flag.go
+1
View File
@@ -10,4 +10,5 @@ var (
Insecure bool
ReadOnly bool
Debug bool
AllowedTools map[string]struct{}
)
pkg/tool/tool.go
+47 -7
View File
@@ -1,7 +1,11 @@
package tool
import (
"slices"
"strings"
"gitea.com/gitea/gitea-mcp/pkg/flag"
"gitea.com/gitea/gitea-mcp/pkg/log"
"github.com/mark3labs/mcp-go/server"
)
@@ -27,12 +31,48 @@ func (t *Tool) RegisterRead(s server.ServerTool) {
}
func (t *Tool) Tools() []server.ServerTool {
tools := make([]server.ServerTool, 0, len(t.write)+len(t.read))
if flag.ReadOnly {
tools = append(tools, t.read...)
return tools
all := make([]server.ServerTool, 0, len(t.write)+len(t.read))
if !flag.ReadOnly {
all = append(all, t.write...)
}
tools = append(tools, t.write...)
tools = append(tools, t.read...)
return tools
all = append(all, t.read...)
if len(flag.AllowedTools) == 0 {
return all
}
filtered := make([]server.ServerTool, 0, len(all))
for _, st := range all {
if _, ok := flag.AllowedTools[st.Tool.Name]; ok {
filtered = append(filtered, st)
}
}
return filtered
}
// WarnUnmatchedAllowedTools logs any names in flag.AllowedTools that don't
// match a tool registered on any of the given domains. No-op if the allowlist
// is empty.
func WarnUnmatchedAllowedTools(domains ...*Tool) {
if len(flag.AllowedTools) == 0 {
return
}
known := map[string]struct{}{}
for _, d := range domains {
for _, st := range d.read {
known[st.Tool.Name] = struct{}{}
}
for _, st := range d.write {
known[st.Tool.Name] = struct{}{}
}
}
var unmatched []string
for name := range flag.AllowedTools {
if _, ok := known[name]; !ok {
unmatched = append(unmatched, name)
}
}
if len(unmatched) == 0 {
return
}
slices.Sort(unmatched)
log.Warnf("Unknown tools in --tools allowlist (ignored): %s", strings.Join(unmatched, ", "))
}
pkg/tool/tool_test.go
+100
View File
@@ -0,0 +1,100 @@
package tool
import (
"slices"
"testing"
"gitea.com/gitea/gitea-mcp/pkg/flag"
"github.com/mark3labs/mcp-go/mcp"
"github.com/mark3labs/mcp-go/server"
)
func makeTool(name string) server.ServerTool {
return server.ServerTool{Tool: mcp.NewTool(name)}
}
func names(sts []server.ServerTool) []string {
out := make([]string, len(sts))
for i, st := range sts {
out[i] = st.Tool.Name
}
return out
}
func TestTools(t *testing.T) {
tests := []struct {
name string
readOnly bool
allowed map[string]struct{}
read []string
write []string
want []string
}{
{
name: "no filters returns write then read",
read: []string{"r1", "r2"},
write: []string{"w1", "w2"},
want: []string{"w1", "w2", "r1", "r2"},
},
{
name: "read-only excludes write",
readOnly: true,
read: []string{"r1", "r2"},
write: []string{"w1"},
want: []string{"r1", "r2"},
},
{
name: "allowlist keeps only listed",
allowed: map[string]struct{}{"r1": {}, "w1": {}},
read: []string{"r1", "r2"},
write: []string{"w1", "w2"},
want: []string{"w1", "r1"},
},
{
name: "allowlist intersected with read-only drops write entries",
readOnly: true,
allowed: map[string]struct{}{"r1": {}, "w1": {}},
read: []string{"r1", "r2"},
write: []string{"w1", "w2"},
want: []string{"r1"},
},
{
name: "allowlist with only unknown names returns empty",
allowed: map[string]struct{}{"unknown": {}},
read: []string{"r1"},
write: []string{"w1"},
want: []string{},
},
{
name: "empty allowlist map passes through",
allowed: map[string]struct{}{},
read: []string{"r1"},
write: []string{"w1"},
want: []string{"w1", "r1"},
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
origRO, origAllow := flag.ReadOnly, flag.AllowedTools
t.Cleanup(func() {
flag.ReadOnly, flag.AllowedTools = origRO, origAllow
})
flag.ReadOnly = tt.readOnly
flag.AllowedTools = tt.allowed
tr := New()
for _, n := range tt.read {
tr.RegisterRead(makeTool(n))
}
for _, n := range tt.write {
tr.RegisterWrite(makeTool(n))
}
got := names(tr.Tools())
if !slices.Equal(got, tt.want) {
t.Errorf("Tools() = %v, want %v", got, tt.want)
}
})
}
}