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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering safety. The description adds valuable behavior beyond those: it requires authentication and 'returns whether the hostname is free', explaining the return semantics. It also clarifies the scope to host/glue records. No contradictions 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.

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

Two tight sentences cover purpose, auth, return value, and workflow position. Every clause earns its place, and the main action is front-loaded. No fluff or repetition of the schema.

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 simple read-only availability check with one required parameter, the description provides everything an agent needs to invoke it correctly: what it does, that auth is required, what the return represents, and when to call it relative to createHost. With no output schema, the return semantics note is sufficient.

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 schema fully documents both parameters. The tool description adds no new parameter meaning; it only repeats that the hostname is a host/glue record, which the schema already conveys with 'Fully qualified host name'. 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 states a specific verb and resource: 'Check if a host/glue record name is available for creation.' It clearly distinguishes itself from sibling tools like checkDomainAvailability and checkKeywordAvailability by specifying 'host/glue record', and it ties to createHost. This is precise and unambiguous.

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 gives clear usage context: 'call before createHost' explicitly tells the agent when to invoke this tool. It also notes the authentication prerequisite. However, it doesn't explicitly say when not to use it or name alternatives (e.g., checkDomainAvailability), so it stops short of a full 5.

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