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

Annotations already declare idempotentHint=true, destructiveHint=false and readOnlyHint=false, so safety is covered. The description adds real value beyond that by disclosing the precondition that renewal requires an unexpired lease and a valid fencing version, warning the agent against a stale-version retry. It still omits what happens to the lease window on success.

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 with the core action front-loaded and the constraint following. Nothing is wasted, though the second sentence is a bare prohibition rather than an actionable routing hint.

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?

A mutation tool with annotations covering the safety profile and no output schema, so return values needn't be described. The precondition is well covered, but the duration_seconds semantics and the resulting lease window are absent, leaving the description only minimally complete for a 4-parameter lease-renewal operation.

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 50%: lease_version and idempotency_key are already documented in the schema, and the description's "fencing version" phrasing merely restates that. task_id and especially duration_seconds (the extension length, default 900, max 3600) receive no explanation anywhere, so the description fails to compensate for the coverage gap.

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 and resource ("Renew your current unexpired lease") and scopes it to the current lease, which distinguishes it from the sibling acquire_task_lease that creates a fresh lease. It does not name the sibling explicitly, so the differentiation relies on the agent inferring the acquire/renew split.

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?

Provides a when-not condition ("Expired or stale leases cannot be renewed"), which is genuine routing guidance. However, it never names the alternative for the expired case (e.g. acquire_task_lease) nor states prerequisites like holding a lease first, leaving the selection implicit.

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