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

No annotations are provided, so the description carries the full burden. It discloses that the tool is a read-only listing operation (membership snapshot), mentions the tier filtering, and includes performance details (latency <100ms) and rate-limit cost. However, it does not explain the 'status' field values or any potential staleness implications beyond the timestamps, which could be important for an agent deciding on data freshness. Still, it adds useful context beyond the schema.

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 well-structured with clear sections for purpose, usage, returns, cost, and latency. It is concise, with each section adding needed information without fluff. The most important info (membership definition) is front-loaded, and technical details are placed in separate labeled blocks for easy scanning.

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?

Given the tool's simplicity (one optional parameter) and the absence of an output schema, the description provides all essential information: what it returns (field names), when to use it, cost, and latency. It could potentially explain the 'status' field values or how to interpret 'first_seen_at' vs 'last_checked_at', but these are minor gaps given the tool's purpose and the clear usage guidance.

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 schema has only one parameter, 'tier', with an enum and default. The description elaborates on the meaning of each tier value: 'attested' includes only vouched keys, while 'all' adds unattested keys with claimed but unverified domains. This goes beyond the schema's bare enumeration, providing the semantic distinction an agent needs to choose correctly.

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 clearly states the tool's purpose: to list the membership of a commons, including signing keys and their vouching domain. It provides specific detail on what each entry contains (key, domain, status, timestamps) and the difference between 'attested' and 'all' tiers. This distinguishes it from siblings like tollbooth_export or tollbooth_stats, which likely handle different operations.

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 includes an explicit 'Use this tool when' section, outlining two concrete scenarios: checking whose data is in the exhibit and verifying an export row's 'site' key. It does not explicitly mention alternatives, but these usage cases are specific enough to guide an agent, and the sibling list contains no direct alternative for this membership listing function.

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