# Web Search Tools Design

**Date:** 2026-04-09
**Project:** `/home/alex/dotfiles`
**Target files:**
- `.pi/agent/extensions/web-search/package.json`
- `.pi/agent/extensions/web-search/index.ts`
- `.pi/agent/extensions/web-search/src/schema.ts`
- `.pi/agent/extensions/web-search/src/config.ts`
- `.pi/agent/extensions/web-search/src/providers/types.ts`
- `.pi/agent/extensions/web-search/src/providers/exa.ts`
- `.pi/agent/extensions/web-search/src/tools/web-search.ts`
- `.pi/agent/extensions/web-search/src/tools/web-fetch.ts`
- `.pi/agent/extensions/web-search/src/format.ts`
- tests alongside the new modules

## Goal

Add two generic pi tools, `web_search` and `web_fetch`, implemented as a modular extension package that uses Exa as the first provider while keeping the internal design extensible for future providers.

## Context

- This dotfiles repo already tracks pi configuration under `.pi/agent/`.
- The current extension workspace contains a tracked `question` extension and small pure helper tests.
- Pi extensions can be packaged as directories with `index.ts` and their own `package.json`, which is the best fit when third-party dependencies are needed.
- The requested feature is explicitly about pi extensions and custom tools, not built-in model providers.
- The user wants:
  - generic tool names now
  - Exa as the first provider
  - configuration read from a separate global file, not `settings.json`
  - configuration stored only at the global scope

## User-Approved Requirements

1. Add two generic tools:
   - `web_search`
   - `web_fetch`
2. Use Exa as the initial provider.
3. Keep the implementation extensible so other providers can be added later.
4. Do **not** read configuration from environment variables.
5. Do **not** read configuration from `settings.json`.
6. Read configuration from a dedicated global file:
   - `~/.pi/agent/web-search.json`
7. Use a provider-list-based config shape, not a single-provider-only schema.
8. Store credentials as literal values in that config file.
9. `web_search` should return **metadata only** by default.
10. `web_fetch` should accept **one URL or multiple URLs**.
11. `web_fetch` should return **text** by default.
12. The implementation direction should be the modular/package-style structure, not the minimal Exa-shaped shortcut.

## Recommended Architecture

Implement the feature as a dedicated extension package at:

- `/home/alex/dotfiles/.pi/agent/extensions/web-search/`

This package will register two generic tools and route both through a provider registry. At runtime, the extension loads `~/.pi/agent/web-search.json`, validates it, normalizes the provider list into an internal lookup map, resolves the configured default provider, and then executes requests through a provider adapter.

For the first version, the only adapter is Exa. However, the tool-facing layer remains provider-agnostic, so future providers only need to implement the shared provider interface and be added to config validation/registry wiring.

This is intentionally more structured than a single-file Exa wrapper because the user explicitly wants future extensibility without changing tool names or reworking the public API later.

## File Structure

### Extension package

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/package.json`
  - declares the extension package
  - declares `exa-js` as a dependency
  - points pi at the extension entrypoint

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/index.ts`
  - extension entrypoint
  - registers `web_search` and `web_fetch`
  - wires together config loading, provider registry, tool handlers, and shared formatting

### Shared schemas and config

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/src/schema.ts`
  - TypeBox schemas for tool parameters
  - TypeBox schemas for `web-search.json`
  - shared TypeScript types derived from the schemas where useful

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/src/config.ts`
  - reads `~/.pi/agent/web-search.json`
  - validates config shape
  - normalizes provider list into an internal map keyed by provider name
  - resolves default provider

### Provider abstraction

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/src/providers/types.ts`
  - generic request and response types for search/fetch
  - provider interface used by the tool layer
  - normalized internal result shapes independent of Exa SDK types

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/src/providers/exa.ts`
  - Exa-backed implementation of the provider interface
  - translates generic search requests into Exa `search(...)`
  - translates generic fetch requests into Exa `getContents(...)`
  - isolates all Exa-specific request/response details

### Tool handlers and formatting

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/src/tools/web-search.ts`
  - `web_search` schema, execution logic, and tool rendering helpers

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/src/tools/web-fetch.ts`
  - `web_fetch` schema, execution logic, and tool rendering helpers

- **Create:** `/home/alex/dotfiles/.pi/agent/extensions/web-search/src/format.ts`
  - shared output shaping
  - compact text summaries for the LLM
  - truncation behavior for large results
  - per-result formatting for batch fetches and partial failures

## Config File Design

The extension will read exactly one file:

- `~/.pi/agent/web-search.json`

Initial conceptual shape:

```json
{
  "defaultProvider": "exa-main",
  "providers": [
    {
      "name": "exa-main",
      "type": "exa",
      "apiKey": "exa_...",
      "options": {
        "defaultSearchLimit": 5,
        "defaultFetchTextMaxCharacters": 12000
      }
    }
  ]
}
```

### Config rules

- `defaultProvider` must match one provider entry by name.
- `providers` must be a non-empty array.
- Each provider entry must include:
  - `name`
  - `type`
  - `apiKey`
- `apiKey` is a literal string in the first version.
- `type` is validated so the runtime can select the correct adapter.
- Exa-specific defaults may live under `options`, but they must remain optional.

### Config non-goals

The first version will **not**:

- read provider config from project-local files
- merge config from multiple files
- read credentials from env vars
- support shell-command-based credential resolution
- write or edit `web-search.json` automatically

If the file is missing or invalid, the tools should return a clear error telling the user where the file belongs and showing a minimal valid example.

## Tool Contract

### `web_search`

Purpose: search the web and return result metadata with a generic surface that can outlive Exa.

Conceptual input shape:

```ts
{
  query: string;
  limit?: number;
  includeDomains?: string[];
  excludeDomains?: string[];
  startPublishedDate?: string;
  endPublishedDate?: string;
  category?: string;
  provider?: string;
}
```

### Default behavior

- returns metadata only
- does not fetch page text by default
- uses the default configured provider unless `provider` explicitly selects another configured provider

### Result shape intent

Each search result should preserve a normalized subset of provider output such as:

- `title`
- `url`
- `publishedDate`
- `author`
- `score`
- provider-specific stable identifiers only if useful for follow-up operations

The tool’s text output should stay compact and easy for the model to scan.

### `web_fetch`

Purpose: fetch contents for one or more URLs with a generic interface.

Conceptual input shape:

```ts
{
  urls: string[];
  text?: boolean;
  highlights?: boolean;
  summary?: boolean;
  textMaxCharacters?: number;
  provider?: string;
}
```

### Input normalization

The canonical tool shape is `urls: string[]`, where a single URL is represented as a one-element array. For robustness, the implementation may also accept a top-level `url` string through argument normalization and fold it into `urls`, but the stable contract exposed in schemas and docs should remain `urls: string[]`.

### Default behavior

- when no content mode is specified, fetch text
- batch requests are allowed
- the default configured provider is used unless overridden

### Result shape intent

Each fetched item should preserve normalized per-URL results, including:

- `url`
- `title` where available
- `text` by default
- optional `highlights`
- optional `summary`
- per-item failure details for partial batch failures

## Provider Abstraction

The provider interface should express the minimum shared behaviors needed by the tools:

```ts
interface WebSearchProvider {
  type: string;
  search(request: NormalizedSearchRequest): Promise<NormalizedSearchResponse>;
  fetch(request: NormalizedFetchRequest): Promise<NormalizedFetchResponse>;
}
```

### Exa adapter responsibilities

The Exa adapter will:

- instantiate an Exa client from the configured literal API key
- use Exa search without contents for `web_search` default behavior
- use Exa `getContents(...)` for `web_fetch`
- map Exa response fields into normalized provider-agnostic result types
- keep Exa-only fields contained inside the adapter unless they are intentionally promoted into the shared result model later

This keeps future provider additions focused: implement the same interface, extend config validation, and register the adapter.

## Rendering and Output Design

The extension should provide compact tool rendering so calls and results are readable inside pi.

### `renderCall`

- `web_search`: show tool name and the query
- `web_fetch`: show tool name and URL count (or the single URL)

### `renderResult`

- `web_search`: show result count and a short numbered list of titles/URLs
- `web_fetch`: show fetched count, failed count if any, and a concise per-URL summary

### LLM-facing text output

The text returned to the model should be concise and predictable:

- search: compact metadata list only by default
- fetch: truncated text payloads with enough context to be useful
- batch fetch: clearly separated per-URL sections

Large outputs must be truncated with the shared truncation utilities pattern used by pi tool examples.

## Error Handling

Expected runtime failures should be handled cleanly and descriptively.

### Config errors

- missing `~/.pi/agent/web-search.json`
- invalid JSON
- schema mismatch
- empty provider list
- unknown `defaultProvider`
- unknown explicitly requested provider
- missing literal API key

These should return actionable errors naming the exact issue.

### Input errors

- empty search query
- malformed URL(s)
- empty URL list after normalization

These should be rejected before any provider request is made.

### Provider/runtime errors

- Exa authentication failures
- network failures
- rate limits
- unexpected response shapes

These should return a concise summary in tool content while preserving richer diagnostics in `details`.

### Partial failures

For batch `web_fetch`, mixed outcomes should not fail the entire request unless every target fails. Successful pages should still be returned together with per-URL failure entries.

## Testing Strategy

The design intentionally separates pure logic from pi wiring so most behavior can be tested without loading pi itself.

### Automated tests

Cover:

1. config parsing and normalization
2. provider-list validation
3. default-provider resolution
4. generic request → Exa request mapping
5. Exa response → normalized response mapping
6. compact formatting for metadata-only search
7. truncation for long fetch results
8. batch fetch formatting with partial failures
9. helpful error messages when config is absent or invalid

### Test style

- prefer pure module tests for config, normalization, and formatting
- inject a fake Exa-like client into the Exa adapter instead of making live network calls
- keep extension entrypoint tests to smoke coverage only

### Manual verification

After implementation:

1. create `~/.pi/agent/web-search.json`
2. reload pi
3. run one `web_search` call
4. run one single-URL `web_fetch` call
5. run one multi-URL `web_fetch` call
6. confirm missing/invalid config errors are readable

## Non-Goals

The first version will not add:

- other providers besides Exa
- project-local web-search config
- automatic setup commands or interactive config editing
- provider-specific passthrough options in the public tool API
- rich snippet/highlight defaults for search
- live network integration tests in the normal automated suite

## Acceptance Criteria

The work is complete when:

1. pi discovers a new extension package at `.pi/agent/extensions/web-search/`
2. the agent has two generic tools:
   - `web_search`
   - `web_fetch`
3. the implementation uses an internal provider abstraction
4. Exa is the first working provider implementation
5. the runtime reads global config from `~/.pi/agent/web-search.json`
6. config uses a provider-list shape with a default provider selector
7. credentials are read as literal values from that file
8. `web_search` returns metadata only by default
9. `web_fetch` accepts one or multiple URLs and returns text by default
10. missing config, invalid config, and provider failures return clean, actionable tool errors
11. core mapping/formatting/config logic is covered by automated tests