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

Annotations already declare the safety profile (idempotentHint=true, destructiveHint=false, readOnlyHint=false), so the description isn't burdened with that. It adds genuine behavioral context the annotations cannot: expired leases are not revived, and the new deadline is computed from now rather than added to the existing one. It doesn't say what happens to leases not owned by the caller, which keeps it below 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?

A single sentence with a front-loaded rationale ('More time for long work:') followed by the precise effect. No filler, no restatement of the title, nothing that could be cut without losing meaning.

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 five-parameter mutation with no output schema, the description plus rich schema annotations and the idempotency/safety hints cover what an agent needs to call it. The main omission is error/edge behavior for leases that are invalid or already expired, which the description touches on only partially.

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 the schema already documents queue, leases, instance_id, passport_token, and visibility_timeout_seconds. The description only re-expresses the timeout semantics ('ends visibility_timeout_seconds from now'), which the schema also states. Baseline 3 is correct.

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 names a concrete action on a concrete resource: it extends queue leases and re-anchors their expiry. The phrase 'each lease that has not run out ends visibility_timeout_seconds from now' makes the operation unambiguously a lease-timer reset. It does not, however, contrast itself with siblings like queue_claim or queue_ack, so it stops short of a 5.

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?

'More time for long work' implies the trigger condition (a consumer needs a lease to survive a slow task), which is useful implied guidance. But there is no explicit when-not, no mention of which leases are eligible or how this relates to queue_ack/queue_nack, and no named alternative. This is implied usage rather than actionable routing.

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