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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-derivable behavior: which link states are ineligible for reactivation, which is an important failure mode an agent can't infer from the schema. It stops short of describing the return payload or permission requirements.

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 tight sentences: the positive effect first, then the exceptions and the fallback. Every clause carries information and nothing is repeated.

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?

An output schema exists, so return values need no explanation, and the eligibility rules plus the code semantics make the definition callable without further reading. Only the absence of explicit sibling routing and permission/auth notes keeps it from being 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% and the single `code` parameter is fully documented, including the full-URL fallback. The description only echoes that the code is preserved, adding no new syntax or format guidance beyond the schema, so 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 (reactivate), the resource (a link), and the exact effect — the same code and destination are restored. That distinguishes it immediately from create/shorten and from update_url, which would change a live link rather than revive a dead one.

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?

Explicitly enumerates the cases where this tool will not work (expired, disabled as unsafe, unassigned custom codes) and points to the alternative, 'create a new link instead'. It doesn't name the sibling tool (shorten_url/create_app_link) that performs the alternative, so the routing is directional but not pinpoint.

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