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

Beyond the readOnly/idempotent annotations, the description discloses real behavioral traits: no credential requirement, aggregate-only with no instance or buyer identifiers, figures suppressed below the calibration minimum sample, and calibration and fingerprint_lineage returned as null while calibration is off. Those are non-obvious output-shaping behaviors an agent could not derive from annotations or schema.

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 action and resource are front-loaded, and the long trailing clause is a dense but load-bearing inventory of what the response contains rather than filler. It is one heavy sentence, though a short break before the null-suppression caveats would read better.

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, so the description must carry the return contract, and it does: it names each section of the payload, explains the null conditions, and confirms no auth is needed. For a single-parameter read tool this leaves nothing an agent needs unresolved.

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 the single slug parameter already carries a pattern, length bounds, and an example. The description restates "by slug" and ties it to the /stores/<slug> URL path, but adds no formatting or lookup nuance the schema does not already supply, so 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?

"Fetch a store's public register entry by slug" gives a specific verb plus resource, and the follow-on enumeration (identity/trust metrics, capabilities, calibration curves, standing, fingerprint lineage) makes the returned object concrete. It never explicitly contrasts itself with the nearby siblings sellers_get or seller_get_me, so an agent must infer that this is the public/aggregate view rather than the private seller profile.

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?

"Works without credentials" and "Aggregates only, no instance or buyer id" imply this is the unauthenticated public lookup path, which is useful situational framing. There is still no explicit statement of when to prefer this over sellers_get or platforms_get, and no exclusion rules, so usage is only implied.

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