tools/call send_email113 accounts blocked · 2 of 5 agents · first seen Sep 11
MCP schema mismatch
The MCP tool declares to as a list of addresses. Agents pass one address as a string, the call fails validation, and the error doesn't say what shape it wants.
- Share of failed tasks
- 14%
- Accounts blocked
- 113
- MRR a month at risk
- $1,130
- Lab trials failed
- 6 of 200
What agents doThe path most agents take, from production and the lab
- The agent lists the toolstools/list → send_email, create_domain, list_templates
- It sends to one address{"to":"ana@example.dev"}
- Validation fails-32602 to: expected array, received string
- It retries the same callSame arguments, same error
- It reports the server as brokenNo email sent
Where it comes from
mcp/tools/send-email.ts:12
12to: z.array(z.string().email()),
In productionAccounts blocked, by the day they made their key
By agent
- claude-code40 · 7%
- codex30 · 8%
- cursor28 · 11%
- gemini-cli15 · 9%
Count, and the share of that agent's API keys it blocked.
Accounts it blocked
Fix
Suggested change
Accept one address or a list in send_email, and describe the field.
What it costs
$1,130/mo
113 blocked accounts × $10 of MRR per working account. New agent-started accounts that reach a working call bring $6,100 of MRR across 610 accounts.
In the labRun 412, failed trials by task
- send1
- domain2
- webhook1
- billing2