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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds genuine value beyond that by enumerating the returned payload (custom fields, status, SMS status, bounce count), which matters because there is no output schema. It does not discuss error behavior for missing/archived members, which the schema's include_deleted hints at but never explains.

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?

A single front-loaded sentence with no filler. The returned-field enumeration is compact and earns its place given the absence of an output schema.

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 simple two-parameter read tool with full schema coverage and read-only annotations, the description covers purpose and return shape adequately. Minor gap: it does not state what happens when the id does not exist or when a member is archived and include_deleted is false.

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 coverage is 100%, including descriptions for both member_id and include_deleted, so the schema carries the parameter burden. The description restates only 'by id' and adds no format, range, or behavioral detail beyond what the schema already provides; 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?

Clear verb+resource ('Get one member') with the lookup key specified ('by id'). This implicitly separates it from emma_find_member_by_email and emma_list_members, though those siblings are never named, so differentiation is inferred rather than stated.

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?

The phrase 'by id' implies the precondition for use, but there is no explicit guidance on when to prefer this over emma_find_member_by_email or emma_list_members. The agent must infer the routing from the parameter name.

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