FastestMCP.Tools.Result (fastest_mcp v0.1.2)

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Canonical tool result helper.

Tool handlers can return plain Elixir values for the common case, but FastestMCP.Tools.Result is the explicit shape when the tool needs:

  • human-readable content that should not be derived automatically
  • structured content for machine consumers
  • result-level metadata
  • an explicit isError flag

When you provide structured_content without content, FastestMCP derives a readable text block from the structured payload so MCP transports still emit a complete tool result.

Examples

FastestMCP.Tools.Result.new("Release checklist generated",
  structured_content: %{status: "ok"}
)

FastestMCP.Tools.Result.new(
  [
    %{type: "text", text: "Release checklist generated"},
    %{type: "text", text: "Warnings: 0"}
  ],
  structured_content: %{status: "ok", warnings: 0},
  meta: %{source: "release-planner"}
)

Summary

Types

t()

Functions

from(result)

Normalizes result-like values into %FastestMCP.Tools.Result{}.

new(content \\ nil, opts \\ [])

Builds a normalized tool result.

to_map(result)

Converts the helper struct into the normalized tool-result map used by the runtime.

Types

t()

@type t() :: %FastestMCP.Tools.Result{
  content: any(),
  is_error: boolean() | nil,
  meta: map() | nil,
  structured_content: any() | nil
}

Functions

from(result)

Normalizes result-like values into %FastestMCP.Tools.Result{}.

new(content \\ nil, opts \\ [])

Builds a normalized tool result.

to_map(result)

Converts the helper struct into the normalized tool-result map used by the runtime.