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

Annotations supply only destructiveHint=true, so the description carries the rest of the burden. It usefully declares the state transition (cancelled back to active) and the endpoint, but says nothing about permissions, idempotency, whether an already-active invoice errors, or what side effects reactivation has on reporting/numbering.

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 short sentences, front-loaded with the action and its effect; nothing redundant. The trailing HTTP method/path adds little for an agent choosing a tool, which keeps it just short of a 5.

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, schema-rich mutating tool with no output schema, the description is minimally sufficient: it identifies the resource and the state change. It omits failure modes and preconditions (non-cancelled invoice, missing series) that an agent would benefit from knowing before invoking.

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 two parameters (series_name, number) are fully documented in the schema. The description adds no extra syntax or format detail beyond what the schema already states, which is the expected baseline.

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?

Specific verb (restore) plus resource (invoice) and the resulting state change (cancelled -> active again), so the agent knows exactly what happens. It does not, however, mention the closely-named sibling smartbill_restore_estimate, so the discrimination from that tool is left to the name alone.

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 precondition phrase 'invoice that was cancelled', which tells the agent this only applies to cancelled invoices. There is no explicit when-not guidance, no mention of restore_estimate as the alternative, and no statement about what happens if the invoice is already active.

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