health_check

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

With no annotations, the description carries the full burden of behavioral disclosure. It details that the tool authenticates once, reuses the cached session, reads the detected API version, and returns a fixed set of keys with specific conditions (e.g., zabbix_api_version is None until a backend connection succeeds, degraded/error results include a detail reason). This provides a complete model of the tool's behavior.

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 front-loaded with a one-line summary, followed by a usage paragraph and then a return-keys breakdown. While longer than typical, every sentence adds value—especially given there is no output schema to explain the return format. The structure is logical, skimmable, and free of fluff.

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 parameterless health-check tool with no output schema, the description is remarkably complete. It explains the exact return keys, possible values, error cases, and behavior (e.g., not scanning problems/items). The agent can confidently invoke it and parse the result without any ambiguity, even without additional structured metadata.

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?

The tool has zero parameters, so schema coverage is trivially 100%. The rubric sets a baseline of 4 for parameterless tools, and the description adds no parameter-specific semantics because there are none. It does clarify that the tool reads environment state (auth can be missing-env), which is useful contextual information.

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 opens with a specific verb+resource statement: 'Report server version, Zabbix connectivity, and configured categories.' This clearly distinguishes health_check from siblings like get_problems, and explicitly notes it does NOT scan problems or items, eliminating any ambiguity about its scope.

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 explicitly states when to call it: 'Call this at session start (or after a tool-call timeout) to confirm the MCP is up...' It also contrasts with heavier operations by noting it is lightweight and does not scan problems or items, giving the agent clear usage context and effectively differentiating it from sibling tools.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.