mpp_phone_finderFind phone numbers associated with an email address, domain, or LinkedIn profile using MPP (Machine Payments Protocol). Pay-per-request, no API key required.
| Name | Required | Description | Default |
|---|---|---|---|
| full | No | Whether to return full phone details | |
| No | The email address to look up | ||
| domain | No | The domain to look up | |
| No | The LinkedIn profile URL |
| 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?
Annotations already carry readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds meaningful behavioral context beyond the annotations by disclosing the payment model and the lack of an API key requirement. It does not contradict the annotations.
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?
Two concise sentences: the first front-loads the verb, resource, and supported inputs; the second conveys the unique billing and authentication characteristics. Every sentence earns its place with no redundancy or filler.
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 tool with an output schema, zero required parameters, and fully described schemas, the description covers the core use case and the MPP-specific nuances. It could be more explicit about requiring exactly one of the three lookup keys, but the 'or' phrasing and the presence of a schema with all-optional properties provide adequate context for most agents.
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%, so the individual parameters are already documented. The description restates the lookup types at a high level but adds no detail about precedence, combination rules, or formatting beyond what the schema already provides. Baseline 3 is appropriate.
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 uses a specific verb ('Find'), names the resource ('phone numbers'), and enumerates the three supported lookup keys (email, domain, LinkedIn profile). It also differentiates from sibling tools by naming the protocol (MPP) and the pay-per-request/no-API-key model, so an agent can distinguish it from plain phone_finder and mpp_phone_validator.
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 when to use this tool: when you want pay-per-request lookups without an API key. However, it never explicitly contrasts it with alternatives like phone_finder or mpp_phone_validator, nor does it state that only one of email/domain/linkedin should be supplied. The guidance is present but largely implicit.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.