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

The description explains that the tool reads a URL and returns a classification, label, and remaining time, which goes beyond the readOnlyHint/destructiveHint annotations. It also frames the tool as a pure explainer, reinforcing that it has no side effects.

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 tightly packed sentences: the first states the resource, inputs, and outputs; the second gives the exact usage trigger. No filler, no repetition of schema fields.

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 one-parameter, read-only inspection tool with no output schema, the description is complete: it tells the agent what input to expect, what the tool will produce, and when to invoke it. The annotations cover the safety profile, so no additional behavioral disclosure is required.

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 coverage is 100%, and the url parameter is already described as 'A countlink.app timer URL.' The description restates the URL expectation but adds little new parameter-specific meaning beyond confirming the URL identifies a CountLink link.

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 'say what it encodes' tied to a concrete resource, countlink.app URLs, and details the exact output: running countdown vs. not-yet-started setup, label, and time left. It clearly distinguishes itself from the create_* siblings by focusing on inspection rather than creation.

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?

It explicitly states when to use the tool: 'when someone pastes a CountLink link and asks what it is or when it ends.' This gives a clear trigger condition, though it does not name alternative tools for contrast or state when not to use it.

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