domain_breachesCheck whether a domain appears in Have I Been Pwned data breaches and identify incidents where the breached service is that domain. No API key required; individual addresses are not listed.
Breaches in HIBP where the breached service is this domain (no key needed). Does not list individual addresses.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safe-read profile (readOnlyHint, openWorldHint), and the description adds two genuinely new facts: no API key/auth is required, and results exclude individual addresses. Return shape, pagination, and result limits remain undisclosed.
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 short sentences, no filler, with the scoping definition and the auth note front-loaded. Every clause carries information.
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 lookup with no output schema, the definition covers what the tool returns conceptually and what it excludes. A brief note on returned fields (breach names/dates) or pagination would close the remaining gap.
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 0% for the single 'domain' parameter, so the description must carry the burden. 'Where the breached service is this domain' does clarify that the argument is the breached service's domain rather than an email domain, but adds nothing about format, validation, or the 3-253 character constraint.
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?
Names a specific resource (breaches) and scopes it precisely: breaches in HIBP where the breached service is this domain. That scope word ('service is this domain') implicitly separates it from email-based siblings, though no sibling is named outright.
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 exclusion 'Does not list individual addresses' usefully tells the agent this is a site-level, not person-level, lookup, and 'no key needed' signals availability. But there is no explicit routing guidance against breach_details or email_breaches, so the agent must infer which to call.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.