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

Annotations already declare destructiveHint=true and idempotentHint=true, so the bar is lower. The description adds meaningful behavior beyond them: patch-style partial mutation, slug immutability, and that the updated link is returned. It does not warn that some fields are wholesale-replaced or removable, but the schema covers that.

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 with zero filler, and the mutation scope constraint is front-loaded before the immutability caveat and the return behavior.

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 an 8-parameter tool with nested objects, the description plus the richly annotated schema covers invocation adequately, and it discloses the return shape even though no output schema exists. Only permissions and the consequences of replacing list-valued fields could be spelled out further.

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% and every parameter carries a detailed description, including replacement and removal semantics for countryRules and socialPreview. The description's only parameter-level contribution is the slug immutability note, so the baseline 3 applies.

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 ("Change an existing link") and adds a hard scope rule that the slug is immutable, which an agent cannot infer from the name. It does not explicitly distinguish itself from create_link or delete_link, but those siblings' names make the split obvious.

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?

"Only the fields you send change" establishes patch rather than replace semantics, which is genuine usage guidance for invoking it correctly. However, nothing says when to prefer this over create_link or delete_link, nor are there stated prerequisites (ownership, permissions).

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