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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It discloses the authorization requirement, a best-practice precaution, the exact return structure, and the specific error codes that may occur. This gives the agent a strong sense of the operation's impact, prerequisites, and failure modes.

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 concise and well-structured with clear sections for requirements, args, returns, and errors. No sentences are wasted, and the info is front-loaded with the core purpose first. The use of code-style examples and error names is efficient and scannable.

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 mutation tool with no output schema, this description is remarkably complete. It covers auth, preconditions, return format, and error handling. The inclusion of a realistic response example and error codes makes the tool's behavior predictable without needing an output schema.

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 0%, but the description fully compensates: slug is defined as 'Site identifier', and new_plan is explained with examples ('site_pro', 'site_managed') and a pointer to list_plans(). This adds meaning far beyond the bare schema property names, especially for the plan slug format.

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 uses a specific verb and resource: 'Change a site's hosting plan (upgrade or downgrade)'. This clearly distinguishes it from sibling tools like create_snapshot, list_plans, and deploy by focusing on plan changes. The parenthetical explicitly covers both upgrade and downgrade directions, leaving no ambiguity about the tool's scope.

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 clear usage context: it states the admin scope requirement and recommends a snapshot before downgrading. It also directs the user to list_plans() to see available plans, which is actionable for choosing the right parameter. However, it does not explicitly state when NOT to use this tool or name alternative tools for other scaling operations.

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