googleapis/mcp-toolbox · error

toolset '%s' not found in prebuilt configuration '%s'. Avail

Error message

toolset '%s' not found in prebuilt configuration '%s'. Available toolsets: %s

What it means

Prebuilt configs are organized as '<source>/<toolset>'. After parsing, LoadConfig looks up the requested toolset in the config's tool groups; if absent, it lists all available toolsets so you can pick a valid one.

Source

Thrown at cmd/internal/options.go:243

				errMsg := fmt.Errorf("unable to parse prebuilt tool configuration for '%s': %w", configName, err)
				logger.ErrorContext(ctx, errMsg.Error())
				return isCustomConfigured, errMsg
			}

			if toolsetName != "" {
				// Legacy toolsets are folded into groups at unmarshal, so the named
				// toolset resolves as a group.
				targetGroup, exists := parsed.Groups[toolsetName]
				if !exists {
					var available []string
					for k := range parsed.Groups {
						if k == "" {
							continue
						}
						available = append(available, k)
					}
					slices.Sort(available)
					errMsg := fmt.Errorf("toolset '%s' not found in prebuilt configuration '%s'. Available toolsets: %s", toolsetName, sourceName, strings.Join(available, ", "))
					logger.ErrorContext(ctx, errMsg.Error())
					return isCustomConfigured, errMsg
				}

				// Filter tools to only include those in the target group
				filteredTools := make(server.ToolConfigs)
				for _, tName := range targetGroup.ToolNames {
					if tCfg, tExists := parsed.Tools[tName]; tExists {
						filteredTools[tName] = tCfg
					}
				}
				parsed.Tools = filteredTools

				// Filter groups to only include the target group
				filteredGroups := make(server.GroupConfigs)
				filteredGroups[toolsetName] = targetGroup
				parsed.Groups = filteredGroups
			}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Use one of the toolsets listed in 'Available toolsets' in the error message
2. Check the toolset spelling and case against the source's docs (e.g. postgres/postgres-sql)
3. Upgrade the toolbox binary if the toolset was added in a newer release

Example fix

// before
--prebuilt postgres/postgres
// after
--prebuilt postgres/postgres-sql

// confirm the toolset exists before invoking
curl -sf http://127.0.0.1:5000/api/toolset | jq 'keys'  # lists available toolsets on a running instance

When it happens

Trigger: Requesting a toolset name that does not exist in the parsed prebuilt config's groups (case mismatch, old toolset name removed, or inventing a name).

Common situations: Using 'postgres/postgres' instead of 'postgres/postgres-sql', or referencing a toolset renamed across toolbox versions.

Related errors

• invalid prebuilt config format '%s'. Did you mean '%s/%s'? U
• failed to check auth requirements: %w
• client authorization is not supported
• error retrieving configuration file: %w
• unable to parse prebuilt tool configuration for '%s': %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/5403d30b0513cb7a. Report an issue: GitHub.