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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered; the description adds genuinely new context: default page size of 25, optional project scoping, and an explicit note that QR codes, secrets and API keys are excluded from the payload. It does not mention auth/permission requirements, which keeps it below a 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?

One dense, front-loaded sentence that leads with the use case and ends with the exclusion. It is efficient with no filler, though the return-field enumeration makes the sentence long and slightly harder to scan.

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 annotations covering the safety profile and an output schema covering return shape, the remaining needs are trigger conditions, pagination behavior and sensitive-field exclusions — all present. Nothing critical is missing for correct invocation.

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 limit, cursor and projectId are fully documented in the schema itself. The description only echoes the 25-per-page default and project scoping, adding no syntax or format detail beyond the schema — the baseline 3 for high coverage.

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 ('list instances' / WhatsApp numbers) and enumerates exactly what comes back (id, name, account name, phone, connection status and health). It also rules out the neighboring operation with 'Not for sending a message', so an agent can separate it from send_message and get_instance without opening a 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?

Gives an explicit trigger ('when someone asks which WhatsApp numbers they have connected... or which ones are offline') plus one exclusion ('Not for sending a message'). It stops short of naming the single-instance sibling (get_instance) as the alternative when the user asks about one number, which is the most likely adjacent intent.

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