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

With no annotations, the description carries the full burden. It usefully discloses deferred behavior — 'Phase 1 stores the preference only' tells the agent this call does not itself trigger an invoice — but omits permission requirements, whether a subscription can be replaced or cancelled, and how repeat calls behave.

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?

Three short sentences, front-loaded with the action and followed by the effect. Tight and waste-free, though the final sentence could be folded into the second.

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 not be described, and the delayed-effect behavior is covered. However, for a 9-parameter, unannotated tool, the near-total absence of parameter meaning leaves the definition short of 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 0% across 9 parameters, so the schema documents none of them, and the description only faintly gestures at delivery_channel via 'chosen channel'. Required fields (reg_number, product_sku), days_before, inn, edo_id and comment are all left unexplained.

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+resource: subscribing to an ITS renewal reminder. It is broadly distinguishable from siblings like check_its_subscription and request_its_renewal_invoice, but does not explicitly contrast itself against those alternatives, 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?

The description implies when it applies ('when the subscription is near expiry') but gives no explicit when-to-use vs alternatives, no prerequisites, and no guidance on the difference from check_its_subscription or request_its_renewal_invoice. Usage is inferable but not spelled out.

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