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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is fully covered. The description adds one genuinely useful behavioral trait: it returns at most the single login-selected account rather than a full list. "Read-only Smartplan Pro API" merely restates the annotations, and nothing is said about auth mechanics or what happens for a multi-account login beyond the stated filter.

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?

Two short sentences, front-loaded with the result-shape constraint before the API-level note. Nothing is padded, though the trailing "Read-only Smartplan Pro API" sentence duplicates annotation content and is the weakest sentence present.

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 zero-parameter, read-only tool with a fully covered schema and no output schema, the description conveys the essential fact an agent needs: the call yields only the login-selected account. Return type (single object vs one-element array) is not pinned down, which is the only notable omission.

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?

The tool takes zero parameters, so there is no parameter meaning to convey, and the schema is empty. Baseline 4 applies; no parameter-related disclosure is needed or missing.

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 gives a specific verb and resource ("Shows ... the account") and adds an important scope qualifier: only the account selected during login, not every account. That resolves the ambiguity created by the "list" prefix. It does not name or distinguish itself from the very similar sibling smartplan_get_account, which is the main remaining gap.

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?

Usage is only implied: the description tells the agent this returns the login-selected account, which implicitly frames when to reach for it. There is no explicit when-to-use/when-not-to-use guidance and no mention of the alternative smartplan_get_account, leaving the agent to infer the split between the two.

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