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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds the useful scope caveat that opening grants no ownership or payment authority, but says nothing about what 'open' returns, whether the object must still be valid, or what happens on an unknown reference.

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?

Two tight sentences with the operation and the scope caveat both front-loaded; nothing is padded. Brevity comes at the cost of coverage, but no sentence is wasted.

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, four optional and undocumented parameters, and a vague verb, the description should explain what is returned and how the reference parameters interact. It does neither, so an agent cannot confidently construct a call from this definition alone.

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 0% across four differently-typed identifiers, and the description mentions only 'plan, task or card' — leaving order_id and view_ref completely unaddressed. Critically, it does not state whether exactly one of plan_id/task_id/order_id/view_ref must be supplied, even though the schema marks none as required.

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 verb 'open' plus the enumerated resources (delegated plan, task, saved card) gives partial specificity, but 'open' is an ambiguous operation — it is unclear whether it reads, resolves, or navigates to the object, and the name 'evuun_app_open' adds nothing. It does not distinguish itself from sibling readers such as evuun_get_capability_task or evuun_get_delegated_payment.

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 clause 'No owner or payment authority' hints at a scope limit but reads as a disclaimer rather than a when-to-use rule. There is no statement of when to choose this over the many sibling get_* tools, nor what to do when a reference is missing.

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