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

Annotations only declare the safety profile (non-read-only, non-destructive, non-idempotent), and the description adds the information that actually matters for calling it: PUSHNOTIF_API_KEY is required, the operation costs 0 credits, and it creates a persistent record. It also discloses the generated artifacts (ECDSA P-256 VAPID keypair, SDK snippet), which cannot be inferred from annotations.

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 dense but front-loaded: the purpose sentence comes first, then usage routing, then constraints and return shape, in that order. Every sentence carries distinct information and none repeats the name or annotations.

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 non-idempotent mutation tool with no output schema, the description supplies auth requirements, cost, persistence, input validation rules, and the exact return JSON shape. An agent has everything needed to call it correctly and interpret the result.

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 100%, so the schema already documents both parameters, including the HTTPS/localhost constraint and the 2–80 character name limit. The description's restatement of the site_url origin rule adds little beyond the schema, so the baseline 3 applies.

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 precise verb and resource ('Register a new website domain or mobile application') plus the concrete side effects (VAPID keypair, HTML SDK snippet). It explicitly names the siblings it is not (update_app_branding, delete_app), so an agent can separate it from every adjacent tool.

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 the positive trigger ('when adding an additional website or app to an existing account') and two explicit exclusions with the correct alternatives for each. Nothing about tool selection is left to inference.

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