Retrieve a subscriber.

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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is fully covered without the description. The description contributes nothing beyond that — no note on whether a missing subscriber errors or returns empty, and no auth or lookup-scope context.

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?

It is a single short sentence, so it is not verbose, but that brevity comes from under-specification rather than discipline. The one sentence merely duplicates the title and earns no place beyond it.

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?

There is no output schema, so the description should ideally indicate what a retrieved subscriber contains or what happens when the id_or_email does not resolve. With no annotations gap to fill and no return-value guidance, the definition is too thin for a lookup tool in a crowded subscriber-tool family.

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 both parameters (account and id_or_email) are already documented in the schema, including the caveat that account is a profile label and not a tenant/provider ID. The description adds no syntax, format, or disambiguation beyond the schema, so the baseline 3 applies.

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?

Tautological: description restates name/title.

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 guidance, no mention of prerequisites, and no reference to alternatives such as list_subscribers for bulk retrieval or create_or_update_subscriber for writes. The agent must guess the boundary between this tool and its many sibling subscriber tools.

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