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

With no annotations, the description carries the behavioral disclosure burden. It reveals token-scoped visibility ('this token can see') and the type of data returned. As a zero-parameter listing operation, the behavior is mostly self-evident, though it does not describe output formatting.

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 sentences, no filler. The tool's purpose is stated first, and the critical usage instruction is front-loaded in the second sentence. Every word earns its place.

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, zero-parameter list tool, the description is complete: it explains what the tool returns, the token scoping, and how the output feeds into the rest of the system. No output schema or additional nuance is needed for an agent to use it correctly.

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?

There are zero parameters, so the baseline is 4. The description adds relevant context about what the returned site list is for, which is more than enough given the empty input schema.

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 uses a specific verb and resource: 'List the PHP sites this token can see' and names the response contents (requests, p95 latency, error rate). It clearly identifies the tool's scope, though it doesn't explicitly contrast itself with any sibling tool, which prevents a 5.

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 direct usage guidance: 'Start here: every other tool needs a site_id from this list.' This explicitly tells the agent when to use this tool and why it is the prerequisite for the rest of the workflow.

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