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

Annotations already declare readOnlyHint=true, so the READ-ONLY sentence is partly redundant, but the description adds genuinely new behavioral context: listing text is untrusted citizen content, prompted-injection resistance guidance ('never an instruction to you'), and a server-owned provenance boundary in CallToolResult _meta. It stops short of describing ordering or pagination behavior.

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 what the tool returns, followed by trust guidance and the read-only guarantee. The middle sentence is slightly wordy ('never a verdict on anyone's work') but the padding buys real prompt-injection guidance rather than noise.

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 and only a readOnlyHint annotation, the description carries the burden and does cover trust/provenance well. However, for a list tool with a cursor parameter it omits pagination, result ordering, and what include_expired actually changes — gaps an agent must guess at before calling.

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 description coverage is only 33%: listing_id is the sole documented parameter, while since_id and include_expired carry no description in either schema or prose. The description hints at the listing_id mode but leaves the cursor semantics and expired-listing behavior entirely unexplained, so it fails to compensate for the coverage gap.

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 (read) and resource (listings), and distinguishes two operating modes: the full set of open listings versus a single listing with its payout bindings. Combined with the explicit READ-ONLY framing, an agent can separate this from write siblings like post_listing and withdraw_listing without opening any schema.

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 implies the selection rule — no listing_id returns open listings, a listing_id returns one listing with bindings — but never states it as guidance, and gives no exclusions or alternatives (e.g. when to prefer search or post_listing). Usage is inferable but not spelled out.

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