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

No annotations exist, so the description carries the full burden. It usefully discloses the return shape (JSON containing the customer id in the "values" object), which is valuable given there is no output schema. However it says nothing about authentication requirements, what happens when no customer matches, or any rate/error behavior.

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 compact lines, front-loaded with the action and the key. The @param/@return tags are slightly redundant scaffolding but they carry content (parameter meaning and return shape) that is not available in the schema, so little 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 single-parameter lookup with no annotations and no output schema, the description covers the input and gives a basic return hint. It still omits not-found behavior and any permission prerequisites, leaving an agent to guess at edge cases, but nothing critical to invoking it 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 0%, but the description compensates by explaining the single parameter: the customer's unique identifier, equated to session_key and typically the session_id. This adds real meaning beyond the bare "identifier: string" schema. Minor ambiguity remains about whether session_key and session_id are interchangeable.

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: "Searches for a customer" plus the lookup key (unique identifier). It is clear what the tool does, though it does not explicitly distinguish itself from sibling customer tools like paywall__customer_create or paywall__customer_get_* beyond the search-by-identifier framing.

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?

No when-to-use or when-not-to-use guidance and no named alternatives. The only usage hint is implicit in "using the unique identifier (session_key)" and the note that the identifier is "typically the session_id," which tells an agent what to pass but not when to reach for this tool.

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