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

Annotations already declare readOnly, idempotent, non-destructive and open-world, but the description adds real context the annotations cannot: the data comes from the board's latest daily probe, token cost is exact in Claude when counted and an estimate otherwise, no connection is made to the servers, and a name missing from the board yields an "unknown" row rather than an error. Only the latency/rate characteristics of the daily probe freshness are left implicit.

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 purpose and alternatives, and every sentence carries information (data source, cost methodology, edge case, format). The middle sentence is a dense run-on enumerating six dimensions, but nothing is redundant.

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?

An output schema exists, so return values need not be described, and the description still covers provenance, the cost-estimate caveat, the unknown-name edge case and the format/structured-content split. Nothing an agent needs to invoke 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%, so baseline is 3, but the description still adds meaning: format selects the text layout only while the structured content is always JSON, and the servers parameter tolerates unknown names (returning an "unknown" row). Those are semantics beyond the schema text.

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 (compares) and resource (two to five registry servers) and enumerates exactly what dimensions are compared: status, client access, tool count, token cost, share of 200k window, initialize latency, cheapest/most expensive/spread. This is clearly distinguishable from lookup_server, search_servers and check_server.

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?

Explicitly states the selecting condition ("Use it to choose between servers that do the same job") and routes to each alternative with its own condition: lookup_server for a full record, search_servers to find candidates, check_server for a URL not in the registry. That is a complete when/when-not/alternatives map.

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