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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds value beyond that: it states what the response deliberately excludes (no endpoint data, no pack prices), confirms the zero-cost, no-auth purchase model, and even gives the HTTP equivalent for parity checking. That is disclosure of real behavioral traits, not repetition of annotated flags.

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?

Two dense sentences front-loaded with the catalog scope and its cost status, with the exclusions and HTTP equivalent trailing as clarifications. Every clause carries information an agent would otherwise have to discover by calling.

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?

There is no output schema and no input schema, so the description bears the full burden of telling the agent what comes back — and it does, by listing the exact fields returned plus what is excluded. For a zero-parameter read of a static catalog, 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. No misleading parameter language is present.

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?

The description names a specific resource (the Agent Data Core pre-computed packs catalog) and enumerates exactly what each entry contains: id, name, buyer job, use-when line, payer category evidence, constituent service ids. That is far more than a restatement of the name. It stops short of a 5 because it never distinguishes itself from the obvious sibling pack_get, which an agent must choose between.

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?

'Free — no payment required, call it directly' tells the agent there is no prerequisite gate before invoking it, which is real usage guidance. What is missing is an explicit routing statement such as 'browse this catalog first, then call pack_get with an id' — the condition that selects this tool over pack_get is only implied by the field list.

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