horizon_check_authVerify a horizOn user session is still valid by checking a userId and sessionToken pair, confirming whether the session remains active.
Checks whether a user session is still valid on horizOn.
| Name | Required | Description | Default |
|---|---|---|---|
| userId | Yes | User ID (UUID) | |
| sessionToken | Yes | Session token (max 256 characters) |
Changes observed during successful MCP inspections.
v1.5.4Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It implies a read-only check but never states whether the session token is consumed, whether a failed check requires re-authentication, or how the result is signaled. For an auth tool with zero annotation coverage this is a meaningful gap.
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?
A single efficient sentence with no waste and the key scope front-loaded. It is arguably too terse for an auth tool, but there is no padding or redundancy.
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?
With no annotations and no output schema, the description must explain what a positive versus negative check returns and what the agent should do on failure. It supplies none of this, leaving the caller unable to interpret results or recover from an invalid session.
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%: userId (UUID) and sessionToken (max 256 chars) are both fully documented in the schema, so the description adds no parameter meaning. Baseline 3 applies when the schema does the heavy lifting.
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 verb ('checks') and resource ('user session validity') on the named platform. It is clearly distinct from the signin/signup siblings, which establish sessions rather than verify them, though it does not name those siblings explicitly.
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?
There is no guidance on when to call this versus the signin/signup/refresh siblings, nor any prerequisite context (e.g. call before operations that require a valid session). The agent must infer usage entirely.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.