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

Goes beyond the annotations by disclosing the replace-all consequence: any feature omitted from the list is removed, and [] clears the plan entirely — a deletion behavior the agent must anticipate. It also explains the idempotent/replace semantics that align with idempotentHint=true, states the tool 'Returns the full plan,' and documents the downstream effect on the pricing table and upgrade dialog.

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?

Front-loads the mutation semantics in the first sentence and then layers routing, flag-gating context, and the return value, with every clause carrying information. It is dense and runs long, but no sentence is filler; a slight trim of the flag-rule aside would make it tighter.

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?

No output schema exists, but the description states 'Returns the full plan,' and it covers the destructive replace semantics, the entitlement/flag interplay, discovery via list_plans, and the get_integration_guide prerequisite. Nothing an agent needs to invoke this correctly is missing.

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 baseline is 3, but the description adds real meaning: an inline example ([{ "key": "analytics", "name": "Analytics" }]), the default of name to key, and the crucial semantic that the array is the complete list rather than an addition, so misleading omission removes features.

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 with exact scope: 'Replace the whole list of on/off features a plan includes.' This verb+resource framing immediately distinguishes it from the sibling single-item mutators add_plan_feature / remove_plan_feature, which the description names explicitly.

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?

Explicitly routes the agent: 'To add or remove one feature and keep the rest use add_plan_feature / remove_plan_feature,' and points to list_plans for discovery and get_integration_guide with topic=billing before writing app code. When-to-use and alternatives are both covered without inference.

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