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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false, so the mutation and safety profile is covered structurally. The description adds real value beyond that by noting the link is returned for re-sending, but it stays silent on what happens to already-collected messages, whether the old link is invalidated, and what occurs when closes_on is omitted.

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?

A single sentence, front-loaded with the action and the two entry states, ending with the return value. No sentence 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?

With no output schema, the description usefully flags that a collecting link comes back, which an agent needs. However, for a state-changing tool it omits the consequences of reopening (message handling, prior link validity) and the behavior when the optional closing date is left out.

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 description coverage is 100%, so both 'book' (handle) and 'closes_on' (date format example) are already documented in structured data. The description adds nothing beyond the schema about the optionality or effect of closes_on — only the title hints at 'a new closing date if there is one'. 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 (reopens) and resource (a book), plus the two triggering states — 'closed or whose date ran out' — and adds that it returns the collecting link. This implicitly distinguishes it from close_collecting, though it never names the sibling outright.

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?

The condition for use is explicit: a book that was closed or whose date expired. There is no exclusion or named alternative, but the trigger state is concrete enough that an agent can act without inference.

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