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

Annotations already cover the safety profile (readOnly=true, destructive=false, openWorld=false), but the description adds substantive context the annotations cannot: metadata is free while execution, entitlement, delivery, and purchased output remain gated, and only 'active public' entries are returned. It does not describe pagination limits or result ordering, so it falls short of 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?

Front-loaded with the key scope constraint in caps, then each subsequent sentence handles one concern (usage, gating, exclusions). Dense but every sentence earns its place; the all-caps opening is slightly heavy-handed.

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 paginated list tool with an output schema present, the description covers scope, gating semantics, and sibling routing, so return-value explanation is correctly omitted. Ordering/filtering guarantees on the returned list are the only notable gap.

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 100% and both parameters (limit, offset) are fully documented with ranges and defaults, so the schema does the heavy lifting. The description's 'page through' phrase reinforces the pagination intent but adds no format or syntax detail beyond the schema. Baseline 3 applies.

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 ('page through') and resource ('active public marketplace capabilities'), and explicitly distinguishes itself from three named siblings (capability.search, offers.list, capability.get). An agent can route correctly 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?

Explicitly states when to use it ('no search filters are needed') and when not to, naming the alternative tool for each exclusion (filtered discovery -> capability.search, CrossingKey offers -> offers.list, exact id -> capability.get). Nothing is left to inference.

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