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

With no annotations, the description carries the full burden and does so well: it discloses destructive replace semantics, that omitting a field clears it, that an empty record clears everything, that invalid input is refused with a reason, a 2 KB size cap per URL, and that `previous` is a host-scoped design id rather than a URL. These are exactly the behavioral traits structured data cannot convey.

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?

Every sentence carries distinct, decision-relevant information and the replace/clear constraint is front-loaded. It is dense and somewhat run-on with em-dashes, but there is no filler to cut.

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 7-parameter, annotation-free mutation with an output schema, the description covers replacement semantics, validation, field formats, and the read-before-write workflow. It stops short of stating permission/auth requirements, which is the main remaining gap.

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 86%, so the baseline is 3, but the description adds real meaning the terse schema fields lack: http/https URL format, the 2 KB per-field limit, and the fact that `previous` is a local design id rather than a URL. It does not address `designId` or the auth `token`, leaving a small gap.

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 precisely what the tool does to the link record ("Replaces the whole record") and enumerates the link kinds it manages (issue, reference, pr, thread, previous). It cleanly separates itself from the sibling read tool ui_builder_get_links, so an agent can tell the write from the read without opening a 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?

It names the alternative explicitly ("read ui_builder_get_links first if you are adding to what is already there") with the condition that selects it, and adds a second directive to record the `pr` when opening a PR for a design built here. Usage is contextualized rather than implied.

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