email_countGet the count of email addresses available for a specific domain. Useful for estimating the potential reach before performing a full domain search.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | The domain to count emails for (e.g., 'example.com') |
| Name | Required | Description | Default |
|---|---|---|---|
| data | Yes |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "additionalProperties": false,
+ "properties": {
+ "data": {}
+ },
+ "required": [
+ "data"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare readOnlyHint=true and openWorldHint=true, covering the basic safety profile. The description adds the domain-scoped counting behavior and the pre-search use case, but does not disclose further behavioral details such as whether the count is approximate, cached, or rate-limited.
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?
The description is two concise sentences with no filler. The action and scope are front-loaded, and the second sentence offers a practical use case in minimal words.
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 single-parameter read-only tool with an output schema, the description covers the essential purpose and usage context. Minor gaps remain: it does not clarify whether the count is exact or estimated, nor does it address the similar mpp_email_count sibling.
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?
Schema description coverage is 100%: the single 'domain' parameter has a type, pattern, and descriptive example. The description's mention of 'a specific domain' adds no additional meaning beyond what the schema already provides.
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?
The description states a specific verb ('get the count') and a clear resource (email addresses for a specific domain), which directly explains what the tool does. It also distinguishes itself from search tools by framing the count as useful before a full domain search.
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 gives clear context: use this to estimate potential reach before performing a full domain search. It implies an alternative approach (domain_search) but does not explicitly name it or state when not to use this tool.
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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