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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description goes further by disclosing what the response contains (all field values, membership level and status) and what the optional flag surfaces (pending order, invoice, allowed actions), which is meaningful behavioral context given there is no output schema.

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 sentences, front-loaded with the action and return contents before the optional-flag detail. The trailing endpoint reference (GET /accounts/{accountId}/contacts/{contactId}) is low value for an agent but is a single clause and does no harm.

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 the burden of describing returns and does so adequately (field values, membership level, status, plus extended info). Nothing critical is missing for a single-resource read tool whose annotations already cover the read-only safety profile.

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 are already documented in the schema, and the description's phrasing about extended_membership_info largely restates the schema's own wording. It adds no format, default, or edge-case detail beyond the schema, making the baseline 3 appropriate.

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 ('Fetch one contact or member') and enumerates the returned data (field values, membership level, status), which implicitly separates it from list_contacts. It stops short of naming a sibling or explicitly contrasting single-record vs list retrieval, so it lands at clear-but-not-differentiating.

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 second sentence implies when the extended_membership_info flag matters (pending membership orders), which is a useful usage cue. However, there is no explicit guidance on when to call this versus list_contacts or update_contact, and no prerequisites or exclusions are stated.

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