web.fetch
Fetch web content from URLs with configurable size and timeout limits while preventing SSRF attacks. Retrieve data safely for local LLM processing.
Instructions
Fetch a URL with size/time limits and anti-SSRF.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | ||
| timeout | No | ||
| max_bytes | No | ||
| headers | No |
Implementation Reference
- src/tools/webFetch.ts:4-22 (handler)Core implementation of the web.fetch tool logic: fetches URL with limits, handles response, extracts text or base64 body based on content type, anti-SSRF implied via fetchWithLimits.export async function webFetch(url: string) { const res = await fetchWithLimits(url, CONFIG.fetchTimeoutMs, CONFIG.maxFetchBytes); if (!res || !res.body) { return { finalUrl: url, status: res?.status || 0, contentType: res?.contentType || 'application/octet-stream', bodyText: null, bytesB64: null, fetchedAt: new Date().toISOString() }; } const ct = (res.contentType || '').toLowerCase(); const isText = ct.startsWith('text/') || ct.includes('html') || ct.includes('xml') || ct.includes('json'); return { finalUrl: res.finalUrl || url, status: res.status, contentType: res.contentType, bodyText: isText ? res.body.toString('utf-8') : null, bytesB64: isText ? null : res.body.toString('base64'), fetchedAt: new Date().toISOString() }; }
- src/server.ts:65-70 (schema)Zod input schema for web.fetch tool parameters.const webFetchShape = { url: z.string().url(), timeout: z.number().int().optional(), max_bytes: z.number().int().optional(), headers: z.record(z.string()).optional() };
- src/server.ts:71-77 (registration)Registration of the 'web.fetch' tool on the MCP server, providing schema, access control (OPEN), and thin wrapper handler.server.tool('web.fetch', 'Fetch a URL with size/time limits and anti-SSRF.', webFetchShape, OPEN, async ({ url, timeout, max_bytes }) => { const res = await webFetch(url); return { content: [{ type: 'text', text: JSON.stringify(res) }] }; } );
- src/server.ts:78-84 (registration)Registration of the 'web_fetch' alias for web.fetch tool.server.tool('web_fetch', 'Alias of web.fetch', webFetchShape, OPEN, async ({ url, timeout, max_bytes }) => { const res = await webFetch(url); return { content: [{ type: 'text', text: JSON.stringify(res) }] }; } );