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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint), so the description's job is picking up what they can't express. It does that by disclosing the content contract — safe metadata, labels, blocked state — and explicitly flagging that credentials are excluded, which tells the agent this call is safe to surface without leaking secrets.

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?

One tight sentence with the access mode front-loaded in parentheses and the exclusion note last. Every clause carries information — resource, returned fields, and the credential caveat.

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 read with no output schema, the description supplies the closest thing to a return contract by enumerating metadata, labels and blocked state, plus the credential exclusion. The only missing piece is the provenance of subaccount_id, which is the one thing an agent must resolve before calling.

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%, so the single parameter subaccount_id carries no documentation anywhere in the definition. The description never explains where this ID comes from (presumably sendpost_list_subaccounts) or its expected form beyond the schema's integer bounds, leaving the agent to infer the linkage.

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 (get) and resource (a single sub-account), and the singular framing implicitly distinguishes it from the sendpost_list_subaccounts sibling that returns many. It does not explicitly name the difference from sendpost_get_subaccount_stats, so it stops short of full differentiation.

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 'READ (account key)' prefix implies this is a non-mutating retrieval and hints at an auth requirement, and 'safe metadata, labels and blocked state' suggests the kind of lookup it serves. But it never says when to prefer this over sendpost_list_subaccounts or sendpost_get_subaccount_stats, nor does it state prerequisites explicitly.

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