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

readOnlyHint=true already establishes this is a safe, non-mutating read, so the description's burden is lower. It still adds useful context: the call is driven by the server-configured key rather than an agent-supplied credential, and it discloses the underlying endpoint (GET /applications/key), which is genuine value beyond the 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 tight clauses: the outcome is front-loaded, the value proposition follows, and the endpoint reference is a compact trailing anchor. 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?

For a zero-parameter, read-only identity tool with no output schema, the description covers what the agent needs to decide to call it. It could briefly characterize the returned application object (id, permissions) but the gap is minor given the simplicity.

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, so the baseline is 4. The description reinforces why — the identity comes from the configured BT-API-KEY rather than an argument — which is the only parameter-relevant information an agent could need.

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 ('Return the application the configured BT-API-KEY belongs to') and makes the identity/whoami nature unmistakable against siblings like basis_theory_get_application or basis_theory_list_applications, which require an explicit id or enumerate resources. The agent can tell what this tool returns without opening anything.

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 clear usage context — 'the fastest way to check which permissions this server actually has' — which tells the agent when this is the right call. It stops short of naming an explicit alternative or exclusion, but the zero-argument, self-scoped nature is implied by 'the configured key'.

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