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

The description explicitly states that it's a change operation (mutation) and explains the side effect: 'The new value applies on the next (re)connection; the live session cache is invalidated so the next tool call uses it.' This is transparent about the behavior and timing, and does not contradict the annotations (readOnlyHint=false, destructiveHint=false).

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?

The description is succinct and well-organized. It conveys all necessary information without fluff, using clear separations for parameter explanations. It earns full marks for conciseness and structure.

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?

Given the tool's simplicity, the description covers purpose, parameters, behavior, and usage guidance comprehensively. There is no output schema, but for a config setter, the description is sufficiently complete for an agent to use it correctly.

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?

The description explains both parameters: 'account' is clarified as which number to target (id/wa_jid, phone, or label; omit if only one is connected), and 'values' is detailed with an example structure and semantics for clearing the proxy with an empty string. This goes beyond the raw schema, providing essential context for correct usage.

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?

The description clearly states the tool's purpose: changing an editable-after-connect setting on a connected number without re-pairing. It explicitly identifies the currently supported field (proxy_url) and its purpose, distinguishing it from other tools like config_get.

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 provides when to use the tool (to change proxy settings on a connected number) and includes practical guidance (recommended to avoid IP bans). It also explains the effect of setting an empty string to clear the proxy, and notes that the value applies on next connection, covering usage nuances.

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