Heffl
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Free tools for AI assistants and developers

Heffl exposes 15 public tools through MCP and a JSON API. No signup, OAuth flow or API key is required.

Available tools

ToolPOST endpoint
Verify an email addressemail_verify/api/public-tools/email/verify
Photography pricingphotography_pricing/api/public-tools/photography/pricing
Freelance hourly and day ratesfreelance_rate/api/public-tools/freelance/rate
Agency pricing and profitabilityagency_pricing/api/public-tools/agency/pricing
Business days and date offsetsbusiness_days/api/public-tools/business/days
Project risk assessmentrisk_assessment/api/public-tools/risk/assessment
Coaching agreement templatecoaching_agreement/api/public-tools/coaching/agreement
Retainer agreement templateretainer_agreement/api/public-tools/retainer/agreement
UAE VAT estimateuae_vat/api/public-tools/uae/vat
UAE corporate tax estimateuae_corporate_tax/api/public-tools/uae/corporate/tax
UAE end-of-service gratuity estimateuae_gratuity/api/public-tools/uae/gratuity
UAE property VAT estimateuae_real_estate_vat/api/public-tools/uae/real/estate/vat
Quotation document dataquotation_generate/api/public-tools/quotation/generate
AI scope of work draftsow_generate/api/public-tools/sow/generate
AI WhatsApp message draftwhatsapp_generate/api/public-tools/whatsapp/generate

Call tools/list for input and output schemas. Calculators return structured numbers; agreement tools return plain text; quotation generation returns document data and a text draft. Visual quotation export is available on the website.

AI scope-of-work and WhatsApp tools return drafts using the server’s existing DeepSeek configuration. They do not send messages. If the provider is unavailable, calls return an error.

Corporate tax accepts already-adjusted taxable income. Property VAT requires an explicit first-supply flag. These scoped estimates do not cover every tax regime or relief.

Connect over MCP

Add this URL in your assistant’s remote MCP connector settings, choose no authentication, and enable the connector for your conversation. Account availability and organization policies vary by client.

https://api.heffl.com/api/public-tools/mcp

The transport is stateless Streamable HTTP. GET and DELETE return 405; POST handles initialization, tool listing and calls. Use an MCP client rather than opening the endpoint in a browser.

Claude supports custom remote connectors with “No sign in.” ChatGPT supports no-auth MCP tools; broad directory distribution requires a separate publishing review. Perplexity supports open-auth remote connectors on eligible accounts. OpenClaw supports outbound MCP configuration. Add the URL using the setup flow documented by your client.

Call the HTTP API

curl https://api.heffl.com/api/public-tools/email/verify \
  -H 'Content-Type: application/json' \
  -d '{"email":"[email protected]"}'

Send exactly one email string. No caller-supplied SMTP host, proxy, port or sender is accepted.

OpenAPI specification · Tool catalog · Plain Markdown documentation

Interpret the result

  • invalid: a definitive format, mail-routing or mailbox failure.
  • unknown: mailbox not checked, unsupported format, timeout, policy block or inconclusive evidence.
  • likely_deliverable: SMTP accepted the recipient and rejected a random recipient. Delivery remains unproven.
  • accept_all: SMTP accepted a random recipient too. Individual mailbox existence remains unproven.

Inspect checks and reason. A disposable, free-provider or role flag is a classification, not a mailbox verdict. SMTP checks are attempted after basic validation: not_checked means none ran. Never tell a user that DNS evidence establishes mailbox existence.

Limits and privacy

30 requests per minute per IP per server instance. AI tools share two calls per minute per client, two concurrent calls, and 100 attempts per day per instance. Email allows up to eight active checks and one check per domain per instance. On HTTP 429, follow Retry-After. MCP capacity errors return isError and a retry message. No bulk endpoint is provided.

The tool does not persist submitted email addresses. Domain routing evidence is cached for one minute. SMTP probes disclose the checked recipient address to its mail server but never submit an email. Network infrastructure may retain request metadata under the Heffl privacy policy.

Discoverability and installation

Public documentation makes the tool understandable to search engines and browsing agents. Registry and client-directory listings are separate publishing steps. A searchable page does not automatically install a tool in an assistant or authorize it to run.

Read the launch guide · Understand verification limits · Assistant integration guide

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