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

Annotations already declare readOnlyHint/idempotent/non-destructive, and the description restates the read-only banner redundantly. It nonetheless adds real context beyond annotations: free cost not counted against tasks, the per-period account quota, that only active accounts are usable, and per-platform primary-account semantics.

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?

Front-loaded with the read-only/cost banner, then behavior, then usage triggers. Dense but each sentence carries information; the read-only restatement slightly overlaps the annotations.

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?

No output schema exists, so the description compensates by listing the returned fields (platform id, name, currency, timezone, active/primary) plus plan and ambiguity semantics. An agent has everything needed to call and interpret it.

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 self-documented. The description notes the platform filter is optional and explains the primary-account concept, but adds no syntax or enum detail beyond the schema — 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?

States a specific verb and resource ('Lists every ad account Adako knows for this user') and enumerates the returned fields. It is clearly distinguished from siblings like switch_primary_account and the platform read tools.

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?

Gives an explicit 'Use when:' clause with concrete triggers (user names an account, or a tool returned account_ambiguous/not_connected). This routes the agent cleanly against alternatives.

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