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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds one genuinely useful behavioral fact not in structured fields: the cost of 1 credit per call. It does not disclose failure behavior (invalid URL, redirect loops, non-redirecting URLs) or whether intermediate hops are returned.

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 short clauses with the action front-loaded and the cost note parenthetically appended. Nothing is redundant and nothing could be trimmed without losing content.

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 single-parameter, non-destructive read tool with rich annotations and no output schema, this is close to sufficient. The remaining small gap is that it never says what comes back (final URL string, redirect chain) or how errors surface, but the annotations and trivial schema carry most of that burden.

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?

Only one parameter exists and schema description coverage is reported at 100%, so the baseline is 3. The description adds the implicit constraint that the url should be one that redirects, but gives no format, protocol, or length guidance beyond what the schema shows.

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 and effect: 'Follow redirects to the final URL.' An agent immediately knows this resolves a shortened/redirecting link to its destination, and the siblings (hash_text, ical_event, qr_code, etc.) are unrelated utilities so no disambiguation is needed. It stops short of naming the input type (shortened URL) explicitly, which keeps it from 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?

There is no explicit when-to-use or when-not-to-use guidance and no mention of alternatives. Usage is only implied by the tool name 'unshorten' and the phrase 'follow redirects', leaving the agent to infer that the input should be a URL that may redirect rather than any URL.

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