accounts_use

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

With no annotations, the description carries the full burden and does well: it discloses a state mutation, the prerequisite, accepted input forms, and the failure mode ('error if no account matches'). It does not state whether the selection persists across sessions or how it interacts with a previously set account, leaving a minor gap.

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 sentences, front-loaded with the core action, then prerequisites/dependents, then input and return behavior. No filler.

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?

There is no output schema, so the description supplies the return contract (resolved account name and id, or an error). Combined with the single documented parameter and explicit prerequisites, nothing needed to call it correctly is missing.

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% and the schema description already explains the UUID-or-prefix format and points to 'accounts_list'. The description repeats this rather than adding new semantics, so the 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 ('Set the active billing account that project commands operate on'), and the scope clause distinguishes it from the accounts_* and projects_* siblings. An agent can tell it selects context rather than creating/listing accounts.

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 prerequisite ('after login'), a conditional ('when you belong to more than one account'), and downstream tools that depend on it ('projects_list', 'projects_create', 'projects_use'). It also names the alternative for discovering valid ids ('accounts_list').

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