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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false; the description goes well beyond them by disclosing the downstream consequence (workspaces lose the entitlement and flags gated on `bridge:billing.entitlement.<featureKey>` turn off), the specific error code, and the return shape ('Returns the full plan'). This is exactly the context needed to decide whether to warn a user before invoking.

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 core action is front-loaded, followed by effects, errors, alternatives, and return value, so an agent gets the essentials immediately. It is a dense block of seven clauses and the trailing get_integration_guide instruction is slightly beyond invocation scope, keeping it just short of a 5.

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 no output schema, the description compensates by stating the return value ('the full plan'), the error behavior, the downstream entitlement effect, the sibling alternatives, and the 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 description coverage is 100% (key, feature, and the optional app param are all documented in-schema), so the baseline of 3 applies. The description confirms that `feature` is matched by feature key and that `key` refers to a plan, but adds no syntax, format, or guidance about the optional `app` override.

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?

Specific verb+resource ('Take an on/off feature off a plan by its feature key') with scope ('other features are kept'). It also names the reciprocal sibling add_plan_feature and list_plans, so an agent can distinguish it from the other plan tools without opening schemas.

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?

Explicit alternatives are given ('Use add_plan_feature to add one and list_plans to see every plan's features'), plus a failure condition (FEATURE_NOT_FOUND) and a prerequisite workflow (call get_integration_guide with topic=billing before writing consuming app code). Both when-to-use and when-not paths are covered.

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