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

Annotations already declare destructiveHint=true, readOnlyHint=false, and idempotentHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: it writes a subscription_events row of type 'renewed', performs cadence-based term-date math, and notes the free-text note lands on the event row and not the subscription. It stops short of mentioning auth/permission requirements or failure modes, so a 4 rather than 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?

It is front-loaded and broken into three short, purposeful parts (what it does, when to use, a concrete example). The example sentence is genuinely useful for an agent but slightly lengthens the definition, so it lands just below the tightest possible phrasing.

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 an output schema present, return values need not be explained, and the description covers purpose, trigger, term math, and param rationale. It omits edge cases such as what happens on an already-renewed or cancelled subscription, leaving a minor gap for a mutation tool.

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 already 100%, so the baseline is 3. The description adds semantic rationale the schema lacks — that optional mrr_cents/seats/plan_name updates exist 'for renewals with uplift' and that opportunity_id should be linked 'when available' — which helps the agent decide whether to populate optional fields.

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 ('Renew a subscription') and immediately scopes the operation: advancing term dates by one cadence, optionally updating MRR/seats/plan, and writing a 'renewed' subscription_events row. This is specific enough that an agent can distinguish it from sibling cancel_subscription without opening either schema.

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 an explicit trigger ('When to use: On close-win of a renewal opp') and clarifies that term-date math is handled automatically by cadence. It does not name or contrast a competing sibling tool (e.g. cancel_subscription), so it stops short of full when-not/alternative guidance.

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