Get subscription by email

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds genuine value by stating the required OAuth scope ('subscriptions:read') and that it reads account data, but it says nothing about behavior on a missing subscription or whether the lookup is case-sensitive on email.

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?

Three short, front-loaded sentences with no filler. The first sentence is redundant with the name, but the auth scope is placed clearly at the end where an agent will find it. Efficient overall.

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 carries more burden than it does: it never indicates what the subscription object contains or what happens when no match exists. For a simple read tool whose annotations cover the safety profile, the auth scope note makes it minimally adequate but not complete.

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%, so the baseline is 3 and the schema does the heavy lifting. The description adds no parameter meaning at all, and notably does not correct the misleading schema description for 'email' ('The ID of the subscriber object'), which conflicts with the tool's email-lookup intent.

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 description repeats the tool name almost verbatim ('Get subscription by email'), so it adds little beyond what the name/title already convey. It does implicitly signal the lookup key (email) which loosely distinguishes it from the sibling get_subscription, but no sibling is named or contrasted. This lands as a vague restatement rather than a sharpened purpose.

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?

There is no when-to-use or when-not-to-use guidance, and no alternatives named (e.g., get_subscription vs. this email-based lookup, or list_subscriptions for enumerating). The only context given is an auth scope, which is a prerequisite rather than usage guidance.

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