agentfootprint/dist/types/tools/hostFilled.d.ts

The explainable agent framework — backtrack a wrong answer to the exact context that caused it (evidence, not guesses). Built on footprintjs.

/**
 * hostFilled — tool arguments the HOST fills, from the run's credential or
 * identity. The model never sees them and cannot set them.
 *
 * ```ts
 * import { hostFilled, fromCredential, fromIdentity } from 'agentfootprint';
 *
 * // An MCP server whose every tool takes a `token` argument:
 * const tools = hostFilled(await crm.tools(), {
 *   token: fromCredential({ service: 'crm' }),   // ctx.credential, resolved per call
 *   tenantId: fromIdentity('tenant'),            // ctx.identity.tenant
 * });
 * ```
 *
 * ── What it does ────────────────────────────────────────────────────────────
 * 1. **Removes the field from the schema the model sees** (`properties` and
 *    `required`). The model is never told the argument exists.
 * 2. **Refuses a model-supplied value by name.** A call that sends the field
 *    anyway — guessed, injected by a document, copied from another tool — is
 *    refused with a result naming the argument, and the tool does not run.
 * 3. **Fills it at the last moment**, inside `execute`, from `ctx.credential`
 *    (the tool's declared `needs`, which `fromCredential({ service })` sets
 *    when the tool has none) or `ctx.identity`. A missing value refuses the
 *    call by name — never an empty or default value.
 *
 * ── Why a wrapper around `execute` ──────────────────────────────────────────
 * The filled value exists only inside the call: the arguments every dispatch
 * door records (`tool_start`, history, the commit log, a consent pause's
 * checkpoint) are the MODEL's arguments, which never held it. Wrapping
 * `execute` makes that true at every door — the agent loop, a resumed call,
 * an inner `ctx.tools` call and `mcpServe` — without each door knowing.
 *
 * A credential value is also SCRUBBED on the way out: every occurrence in the
 * tool's result is replaced by `[host-filled]`, and a thrown error that
 * carries it (an SDK that echoes its request) is replaced by one that does
 * not. That is defence in depth for a server that echoes; it cannot cover a
 * value the tool transforms (base64, hashing) or sends elsewhere itself.
 * Identity values are not secrets and are not scrubbed.
 *
 * Pattern: Decorator over `Tool` (declaration + execute). Role: tools, argument law.
 */
import type { Credential } from '../identity/types.js';
import type { HostFilledArguments } from '../semantics/coverage/search/inEffect.js';
import { type Tool } from './tools.js';
/** Which identity field a {@link fromIdentity} fill reads. */
export type HostFilledIdentityField = 'principal' | 'tenant' | 'conversationId';
/** Fill from the call's resolved credential (`ctx.credential`). */
export interface HostFillFromCredential {
    readonly from: 'credential';
    /** The service (`needs.credential`) — required when the tool declares no `needs`. */
    readonly service?: string;
    /** Scopes / mode for the `needs` this fill declares (ignored when the tool has its own). */
    readonly scopes?: readonly string[];
    readonly mode?: 'machine' | 'user';
    /** Credential → argument value. Default: a bearer's `token`, an API key's `key`. */
    readonly read?: (credential: Credential) => string;
}
/** Fill from the identity the run's caller named (`ctx.identity`). */
export interface HostFillFromIdentity {
    readonly from: 'identity';
    readonly field: HostFilledIdentityField;
}
/** Where a host-filled argument's value comes from. */
export type HostFill = HostFillFromCredential | HostFillFromIdentity;
/**
 * Fill the argument from the call's credential. With `service`, the tool's
 * `needs` is declared for you (a tool that already declares one must name the
 * same service, or omit `service`).
 */
export declare function fromCredential(options?: Omit<HostFillFromCredential, 'from'>): HostFillFromCredential;
/** Fill the argument from the identity the run's caller named. */
export declare function fromIdentity(field: HostFilledIdentityField): HostFillFromIdentity;
/**
 * A model sent a value for an argument the host fills. The call is refused
 * and the tool does not run. Names the arguments, never a value.
 */
export declare class HostFilledArgumentError extends Error {
    readonly toolName: string;
    readonly fields: readonly string[];
    readonly code: "ERR_HOST_FILLED_ARGUMENT";
    constructor(toolName: string, fields: readonly string[]);
}
/**
 * A host-filled argument had no value for this call — no credential was
 * resolved, the credential has no single value to read, or the run's caller
 * named no such identity field. The call is refused; nothing is guessed.
 */
export declare class HostFilledValueMissingError extends Error {
    readonly toolName: string;
    readonly field: string;
    readonly code: "ERR_HOST_FILLED_VALUE_MISSING";
    constructor(toolName: string, field: string, why: string);
}
/**
 * Which arguments `hostFilled` fills on `tool`, by where their value comes
 * from — the names only, never a value. `undefined` for a tool no
 * `hostFilled` returned.
 *
 * The filled values exist only inside `execute`, so the arguments every door
 * records never hold them; a reader that composes ground from a call's
 * arguments (`Tool.search` composition) learns the filled set here: an
 * identity-filled argument is a filter in effect, a credential-filled one
 * names no ground.
 *
 * @example
 * ```ts
 * hostFillsOf(hostFilled(tool, { tenantId: fromIdentity('tenant') }));
 * // { identity: { tenantId: 'tenant' }, credential: [] }
 * ```
 */
export declare function hostFillsOf(tool: Tool): HostFilledArguments | undefined;
/** What replaces a credential value in a result or an error. */
export declare const HOST_FILLED_PLACEHOLDER = "[host-filled]";
/**
 * Declare tool arguments as filled by the host.
 *
 * One tool: every named argument must be a property of its `inputSchema`.
 * A list (e.g. `mcpClient().tools()`): each tool takes the fills for the
 * arguments IT declares and is returned unchanged when it declares none; an
 * argument no tool in the list declares is refused (a typo would otherwise
 * hide nothing).
 *
 * @throws TypeError at build — an unknown argument, a fill that is not one,
 *   a credential fill with no service on a tool that declares no `needs`, a
 *   service that disagrees with the tool's own `needs`, or an argument the
 *   tool also declares under `wants` / `askOrAssume`.
 */
export declare function hostFilled<T extends Tool>(tool: T, fills: Readonly<Record<string, HostFill>>): Tool;
export declare function hostFilled(tools: readonly Tool[], fills: Readonly<Record<string, HostFill>>): readonly Tool[];
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