List Switchable Accounts

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is known. The description adds valuable context on the underlying data source (Facebook's account switcher), what identities are included, and the return structure, going beyond the annotation defaults.

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?

The description is three concise sentences plus a return structure line. It leads with the core purpose, then the source and scope, then the returned shape. No fluff or redundancy.

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 read-only, no-parameter list tool with an output schema, the description fully covers purpose, scope, source, and return value. It includes a note that it's the discovery source, which completes the behavioral context. Nothing critical 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?

The tool has zero parameters, and schema description coverage is 100% vacuously. Per the rubric, 0 params earns a baseline of 4; the description also notes the return format, which is useful given no inputs.

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 uses a specific verb 'Discover' and clearly identifies the resource: every identity the logged-in session can switch to. It distinguishes itself from siblings by naming the source, the account switcher, and the contents: Pages, linked profiles, and the user profile itself.

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 description explicitly states its role: 'This is the discovery source an agent uses to learn which identities exist for this session.' This implicitly tells the user when to use it, but it doesn't mention when not to use it or name alternatives like get_me or list_accounts, which slightly weakens the guidance.

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