Have I Been Pwned

Have I Been Pwned - Breaches

hibp_list_breaches

Read-onlyIdempotent

List public HIBP breaches, optionally filtered by domain, spam-list flag, and verification status.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`limit`	No	Maximum number of items to include in the response. Defaults to 25.
`domain`	No	Filter to breaches for a specific domain.
`offset`	No	Number of items to skip before returning results. Defaults to 0.
`isSpamList`	No	Filter to breaches that are or are not flagged as spam lists.
`response_format`	No	Format only the text content as markdown (default) or a JSON string. The same machine-readable data is always returned in structuredContent.	markdown
`includeUnverified`	No	Include unverified breaches. Defaults to true.

Output Schema

TableJSON Schema

Name	Required	Description
`limit`	No
`offset`	No
`hasMore`	No
`message`	No	Present when the tool returns an error.
`breaches`	No
`guidance`	No	Additional guidance for resolving the tool error.
`nextOffset`	No
`statusCode`	No	Present when the tool returns an error.
`totalCount`	No
`returnedCount`	No
`rateLimitResetAt`	No	UTC timestamp indicating when the current rate limit window should have reset.
`retryAfterHeaders`	No	Retry headers that mirror the standard HTTP rate-limit response when applicable.
`retryAfterSeconds`	No	How long to wait before retrying, when the tool is rate limited.

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedAug 27, 2026

changedInput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

changedInput schema / properties / response_format / description

Previous value: -"Format the text response as markdown (default) or JSON. structuredContent is always returned."New value: +"Format only the text content as markdown (default) or a JSON string. The same machine-readable data is always returned in structuredContent."

changedOutput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

First observedJul 23, 2026

TDQS

A3.6/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds little beyond the schema: 'public' is a mild contextual cue, but rate limits, pagination behavior, or the meaning of verification status are not disclosed. No contradiction with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single, front-loaded sentence that communicates the core action and available filters without filler. It is appropriately compact for a tool with a well-documented schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 0 required parameters, a complete output schema, and full parameter documentation in the input schema, the description is sufficient for an agent to invoke the tool correctly. Missing sibling-differentiation guidance is a minor gap given the already-strong structured context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema carries the parameter documentation. The description names three filter dimensions (domain, spam-list flag, verification status) which loosely maps to domain, isSpamList, and includeUnverified, but it adds no new meaning beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's function: list public HIBP breaches, with optional filtering by domain, spam-list flag, and verification status. The verb 'List' and plural 'breaches' distinguish it from single-breach retrieval tools like hibp_get_breach, though it does not explicitly name or contrast siblings.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies this is the tool for retrieving multiple breaches and optionally filtering them, which is a reasonable usage signal. However, it provides no explicit when-to-use guidance, alternatives, or exclusions such as when to prefer hibp_get_breach or hibp_get_latest_breach.

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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