SignNow MCP has 11 tools with consistent naming (verb_noun pattern) and basic descriptions. However, parameter descriptions are minimal or absent for most tools, and output schemas are not formally documented. Error handling returns JSON with error fields but lacks recovery guidance. No tool annotations (readOnlyHint, destructiveHint) despite clear risk classifications. Descriptions average ~80 chars (below 194-char baseline), and many parameters lack type constraints (e.g., 'role' in add_signature_field is free-form string, not enum). The server is functional but falls short of production-grade quality.

• Add parameter descriptions to all tools. For 'role' in add_signature_field, specify: 'Signer role name (e.g., "Signer 1", "Signer 2"). Must match a role defined in the document.' For 'event' in register_webhook, use an enum: ['document.complete', 'document.update'].
• Implement tool annotations via FastMCP. Mark read-only tools (get_document, list_documents, list_templates) with readOnlyHint=true. Mark destructive tools (cancel_invite, delete operations) with destructiveHint=true. Mark idempotent tools (create_from_template) with idempotentHint=true.
• Document output schemas in tool definitions. For get_document, declare: 'Returns {id, document_name, page_count, created, updated, roles: [{name, id}], field_invites: [...], signatures: [...]}'.
• Add validation and recovery hints to error messages. E.g., 'File not found: /path/to/file. Ensure the path is absolute and the file exists.' For API errors, suggest: 'Upload failed: 401 Unauthorized. Check that SIGNNOW_API_TOKEN is set correctly in .env.'
• Constrain free-form parameters with enums or regex patterns. For 'event' in register_webhook, use enum=['document.complete', 'document.update']. For 'role', document the expected format and provide examples of valid role names from the document.