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

Annotations already declare non-destructive, idempotent behavior, so the description adds value beyond that: Pro-plan gating, that rules/tags replacements overwrite prior state, that bots always get the base URL and are not counted, and that the short code is preserved. It doesn't state permission/auth requirements or reversibility explicitly, keeping it from 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?

The main capability is front-loaded in the first sentence, with the Pro-only features grouped afterward. The parenthetical WhatsApp example is illustrative but slightly decorative, and the sentence is dense; still, every clause maps to a real capability, so waste is minimal.

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 13-parameter mutation tool with nested objects and no output schema, the description covers all the major intents (redirect, expiry, rules, scheduling, fallback) and notes the key invariant that the code is unchanged. It leaves auth/permission context and the exact non-Pro vs Pro boundary for tags unaddressed, so it is strong but not fully complete.

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 100%, so the schema already documents every parameter including the nested rules and unavailable_page shapes. The description mostly restates those capabilities (destination rules, activation date, click limit) at a higher level without adding syntax or format detail beyond the schema, so baseline 3 is appropriate.

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 opens with a specific verb and resource ('Change where a link points') and then enumerates exactly what can be updated: destination, expiry, destination rules, activation date, click limit, and unavailable page. This is clearly distinct from create_link, delete_link, and get_link without naming them.

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 gives strong context on what kinds of edits this tool handles and flags which capabilities require the Pro plan, plus the useful reassurance that the short code stays the same. It stops short of explicitly naming alternatives (e.g. use delete_link to remove a link entirely) or stating when-not to use it, so it misses a 5.

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