check_certificateReads the HTTPS certificate of a public domain and reports days until expiry, the expiry date and the issuer.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | Domain to inspect, e.g. "example.com". |
| Name | Required | Description | Default |
|---|---|---|---|
| state | Yes | ||
| domain | Yes | ||
| issuer | Yes | ||
| validTo | Yes | ||
| daysRemaining | Yes | Negative once expired |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "daysRemaining": {
+ "description": "Negative once expired",
+ "type": "number"
+ },
+ "domain": {
+ "type": "string"
+ },
+ "issuer": {
+ "type": [
+ "string",
+ "null"
+ ]
+ },
+ "state": {
+ "enum": [
+ "valid",
+ "expiring soon",
+ "EXPIRED"
+ ],
+ "type": "string"
+ },
+ "validTo": {
+ "type": "string"
+ }
+ },
+ "required": [
+ "domain",
+ "daysRemaining",
+ "validTo",
+ "issuer",
+ "state"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description usefully adds that the tool performs a live read of a public domain's HTTPS certificate, but it does not surface failure modes, latency, or other behavioral nuances beyond what annotations and the output schema already convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
One concise, front-loaded sentence that names the action, the resource, and the key outputs without filler or restating the tool name. Every phrase earns its place.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a one-parameter, read-only, idempotent tool with an output schema and safety annotations, the description is sufficient for correct invocation. It does not cover edge cases or alternative tool selection, but the low complexity and existing structured metadata make this acceptable.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema fully documents the single `domain` parameter with an example, giving 100% coverage. The description adds only the qualification 'public domain' and ties the parameter to HTTPS certificate retrieval, which is marginal extra meaning beyond the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific action (Reads), resource (HTTPS certificate of a public domain), and expected outputs (days until expiry, expiry date, issuer). This clearly distinguishes it from sibling tools like check_site or list_outages, which concern site status rather than certificate details.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies the tool is for certificate-expiry checks, and the sibling names make it inferable that check_site covers availability. However, it does not explicitly say when to prefer this tool over alternatives or when not to use it, leaving the selection to inference.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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