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

No annotations are provided, so the description carries the full behavioral burden. It does add useful behavior beyond the schema: input normalization (http/https, www, trailing slash) and what is returned when a match is found. It does not state what happens on a miss, whether auth is required, or any rate limits.

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?

Three short sentences, zero filler, and the core purpose is front-loaded before the normalization and return-value details. Every sentence 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 1-parameter read tool with no output schema and no annotations, the description covers purpose, normalization, and return content well. The only meaningful gap is the not-found / no-match outcome, which the agent would need to know.

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% for the single 'url' parameter, so the baseline is 3. The normalization note hints at how the input is matched, but the description adds no format or syntax detail beyond what the schema already documents.

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 (check/lookup) and resource (existing b59.link short URL), which is unambiguous on its own. It implicitly contrasts with the create-style sibling shorten_url, but never names or explicitly rules out siblings such as shorten_url or get_stats_url.

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?

Usage is implied by the description's 'check whether a URL already has a short URL', so an agent can infer this is a pre-shortening / dedupe lookup. However, there is no explicit when-to-use or when-not-to-use guidance, and no alternative tool (e.g., shorten_url when no match exists) is named.

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