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

Annotations give the safety profile (idempotent, non-destructive), and the description adds consequences not in those annotations: nulling path keeps the short address, pausing makes visitors hit the not-found page, and QR codes survive a destination change. That is real behavioral value, though the effect on existing fields not passed is unstated.

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?

Two sentences with no filler, front-loaded on the verb and the id source. The parentheticals are dense but each adds a useful behavior; the sentence is long and slightly run-on but nothing is wasted.

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 15-parameter mutation with a nested destination object, no output schema, and only 33% schema coverage, the description should cover more parameters. It handles the highest-risk semantics (path null, is_active, QR behavior) but leaves several parameters and the required site_id/link_id pairing largely to the schema.

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?

With only 33% schema coverage the description has to carry meaning, and it does well for path (null semantics), is_active (pause behavior), destination and campaign tags. But label, fallback_url, forward_query, tag_destination, user_goal and description get no explanation anywhere, so the compensation is partial.

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?

Specific verb ("Change") plus resource ("one tracked link by its id") and an explicit enumeration of the updatable fields. An agent can tell this apart from create_link, remove_links and update_redirect without opening another schema. The reference to list_links for the id also grounds the resource.

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 tells the agent where the id comes from (list_links) and gives conditional guidance: null path removes the on-domain address, is_active:false pauses and shows visitors the not-found page. There is no explicit when-not or sibling contrast against update_redirect/suggest_link, which keeps it below a 5.

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