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

Annotations already cover read-only/idempotent/closed-world, yet the description adds meaningful behavior: the server is stateless, the X-YHYS-Test header must be sent on every request, and the ping may refresh research vintage (a side effect for a read tool). The toolStats/toolStatsExternal/toolStatsInternal and clientInfo.name prefix sentences are opaque and add bulk without clarifying invocation behavior, keeping this below a 5.

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 purpose and the call-to-check_position guidance are front-loaded, which is good. But the middle block about toolStats buckets and yhys-qa/yhys-feel clientInfo prefixes is dense internal jargon that consumes attention without helping an agent decide to call or how.

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?

With no output schema, the description carries the return-value burden and does list the main response fields (status, version, schemaVersion, policyVersion, feature flags, tool list) plus the stats buckets. It stops short of describing field shapes, but covers enough for a zero-param health probe.

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?

Zero parameters, so the baseline of 4 applies. The only invocation-relevant detail is the required X-YHYS-Test header, which is disclosed in prose even though it isn't in the schema (additionalProperties: true).

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+resource ("Liveness and capability check for yieldsentinel") and enumerates what it returns: status, package version, schemaVersion, policyVersion, feature flags, and available tools. It explicitly separates itself from the sibling by noting "a verdict still requires check_position."

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?

"Use this first to verify connectivity, then call check_position with policyPreset treasury-conservative | balanced-research | rwa-selective" gives an explicit ordering, the alternative, and even the downstream parameter values. The caveat "YH healthy ≠ YS ok" tells the agent this is a precondition check, not a verdict.

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