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

With no annotations, the description carries the full behavioral burden and does disclose a real downstream consequence: inactive subscriptions drop out of upcoming payment calculations and summary totals. It also states the required finance:write scope. It stops short of saying whether the change is reversible, idempotent, or what happens to already-generated payment records.

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, then the side effect, then the permission requirement. Every sentence earns its place with no redundancy.

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 two-parameter toggle with no annotations and no output schema, the description covers the action, the downstream data effect, and the auth requirement, which is enough to invoke it correctly. Only a note on reversibility or error behavior is missing.

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% and both parameters (id, isActive) are already documented in the schema with clear semantics, so the baseline of 3 applies. The description adds no syntax or format detail beyond what the schema provides.

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 pair (activate/deactivate) and resource (subscription), so the operation is unambiguous. It does not, however, distinguish itself from the sibling update_subscription, which an agent could reasonably assume also flips the isActive field.

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?

Usage is implied by the name and description (use it to flip active state), but there is no explicit when-to-use guidance or contrast against update_subscription or delete_subscription. The prerequisite (finance:write scope) is stated, which helps but is an auth constraint rather than a usage rule.

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