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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, and the description adds material behavior the annotations cannot convey: the federated live query to upstream registries, ranked fusion, the fact that the returned score is relevance only and not a trust or safety signal, and that payment terms come from the publisher manifest or the endpoint's own 402 with the caller paying the provider directly.

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 does and immediately followed by the return shape and a critical caveat about the score's meaning. Dense but every sentence carries distinct information; no filler.

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-shape burden and does it: ranked matches, relevance score, endpoint to connect to, and which registries carry each result. Combined with payment-term provenance, an agent has enough to call and interpret this tool correctly.

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 86%, so the baseline is 3, but the description adds real semantic depth the schema lacks: the distinction between 'free' (none known) and 'payable' (price or 402 known), the source of price terms, and direct caller-to-provider payment. It says nothing about 'kind', 'limit', 'federate' or 'network' beyond the schema.

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 and resource ('Search for an MCP server, skill, agent, API or other callable capability for a task') and precisely scopes it ('across this index and every other public ARD registry at once'). It never names or contrasts the sibling find_tool, so an agent must infer the split between the two finders.

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?

Usage is implied rather than stated: the description covers payment filtering and price caps, suggesting when those filters matter, but gives no explicit guidance on when to use this over find_tool or registry_stats. No prerequisites or exclusions are named.

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