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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the write/idempotency profile is covered structurally. The description adds the domain (b59.link) and the return payload (short URL plus stats URL), but says nothing about auth requirements, collision behavior when a custom slug is taken, or why the operation is idempotent.

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, front-loaded with the primary action and outcome, with the optional parameter and return values following in order of relevance. Nothing is padded or redundant.

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 two-parameter tool with no output schema, the description usefully discloses what comes back (short URL and stats URL) and the target domain, which an agent needs to chain into get_stats_url. The main gap is the absence of any authentication or error-condition context.

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%: the url and slug parameters, including the slug's character set and 100-char limit, are already fully documented in the schema. The description only restates that the slug is optional and that a random one is used otherwise, adding no new semantics.

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 resource ('Shorten a long URL'), names the concrete product outcome (b59.link short URL), and clarifies the custom-slug option. It is distinguishable from lookup_url and get_stats_url, though it never names a sibling to draw the boundary explicitly.

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 purpose - an agent can infer this is the creation step - but there is no explicit when-to-use guidance, no mention of prerequisites such as authentication, and no comparison to lookup_url or create_tracker for retrieving or managing existing links.

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