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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), but the description adds genuinely non-obvious behavior: in app-capable hosts the result renders as an interactive panel, and the agent must not duplicate its contents in the reply. That host-dependent rendering rule is not inferable from schema or annotations.

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 sentences, zero filler, front-loaded with the resource and the field the agent should act on. The second sentence is dense but each clause (panel rendering, don't duplicate, add only missing info) carries distinct guidance.

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, so the description carries the burden of indicating what comes back; it names plan, Stripe subscription state, and the isActive flag, and explains how the result is surfaced. It could say more about edge cases (e.g., no subscription present), but it is sufficient for a zero-parameter read.

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 tool takes zero parameters and schema coverage is 100%, so there is nothing for the description to clarify. Baseline 4 applies for a no-argument tool.

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 ('Get plan and Stripe subscription state') plus the key field of interest ('isActive'). It is distinguishable from related siblings like get_credits and get_accounts, though it does not name them 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?

Gives a concrete triggering condition ('check isActive before scheduling posts'), which tells the agent when this call matters. It stops short of naming an alternative tool or stating when not to call it.

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