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

Annotations declare destructiveHint=true and openWorldHint=true; the description earns credit for disclosing the actual destructive vector — 'Incomplete metadata of an existing link may be refreshed and replaced' — which the agent would not know from annotations alone. It does not cover auth requirements, rate limits, or what the add-to-library flow does on duplicates, so it falls short of a 5.

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 sentences, front-loaded with the action and immediately followed by the disambiguation that matters most. Dense and largely waste-free, though the closing back-compat note is slightly tangential to task selection.

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 mutation tool with a destructive hint, an output schema (so return values need no explanation), and zero required parameters, the description covers the key risk and the sibling boundary. The remaining gap is the semantics of `completed` and `async_labeling`, which an agent invoking with defaults would want to understand.

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 0%, so the description carries the full burden across 5 parameters. It gives real meaning for link, book_id (deprecated for back-compat) and implicitly resource_name, but says nothing about `completed` or `async_labeling` (default true), leaving two parameters entirely unexplained.

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 ('Adds a non-book web link or an existing named resource') and scopes it to 'the signed-in user's Linko library.' It explicitly names the sibling it is not (add_book) and the condition that routes to it, so an agent can distinguish the two without opening either schema.

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?

Gives an explicit exclusion and the alternative: books go through add_book with title/author/ISBN/catalog id, 'not as a link to a book page.' It also explains the book_id parameter's backwards-compatibility status, which tells an agent when to prefer link over book_id.

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