Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
git clone --depth 1 https://github.com/ZapSign/api-mcpWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/rules/zapsign/api-mcp/tool-pattern)<a href="https://agentmods.dev/rules/zapsign/api-mcp/tool-pattern"><img src="https://agentmods.dev/badge/rules/zapsign/api-mcp/tool-pattern/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/rules/zapsign/api-mcp/tool-pattern"><img src="https://agentmods.dev/badge/rules/zapsign/api-mcp/tool-pattern.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00000 | $0.00525 |
| Opus 5.5 | $0.00000 | $0.00210 |
| Sonnet 5.5 | $0.00000 | $0.00105 |
| Haiku 4.5 | $0.00000 | $0.00052 |
Grade A, and why
tool-pattern scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
Tool Implementation Pattern
File Structure
- Each file exports ONE function:
registerXxxTool(server: McpServer): void - The registry (
src/tools/registry.ts) is the ONLY file that imports tool modules
Required Imports
McpServerfrom@modelcontextprotocol/sdk/server/mcp.jsgetMcpAuthContextfromagents/mcpZapSignClientfrom../../api/clientformatToolSuccess,formatToolErrorfrom../../utils/tool-responseAuthPropsfrom../../auth/typesZapSignMcpErrorfrom../../errors/baserequireScopefrom../../utils/scope- Schemas from
./schemas
server.registerTool() Call
Use registerTool (NOT deprecated server.tool()):
server.registerTool('tool_name', { title, description, inputSchema: XxxSchema.shape, annotations: { readOnlyHint, destructiveHint, idempotentHint, openWorldHint: true } }, handler)
Handler Pattern (5 steps)
const auth = getMcpAuthContext()— no generic (SDK does not support it)- Guard:
if (!auth) return formatToolError('Authentication required...') const props = auth.props as unknown as AuthProps— cast needed, SDK types props as RecordrequireScope(props.grantedScope, 'scope:level')— enforced per toolconst client = new ZapSignClient(props.zapSignApiUrl, props.zapSignApiToken)const result = await client.method(args)return formatToolSuccess(JSON.stringify(result))— compact JSON, no pretty-print
Error Handling
- Catch
ZapSignMcpError→formatToolError(error.message) - Catch unknown →
formatToolError('An unexpected error occurred') - NEVER throw from a tool handler — always return formatToolError
Annotations (required on every tool)
readOnlyHint: true for GET tools, false for write toolsdestructiveHint: true only for DELETE toolsidempotentHint: true for GET and PATCH toolsopenWorldHint: true (all tools call external ZapSign API)title: human-readable name for Claude.ai display
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 48 lines · 0 tokens per session scan A 56feba05cf58
tool-pattern is a cursor rule published in the GitHub repository ZapSign/api-mcp (1 stars, last pushed 7d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 525 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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