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

Annotations already declare a safe read profile (readOnly, idempotent, non-destructive, not open-world), so the bar is lower. The description adds real context beyond annotations: rows exist only because a fetch produced them, nothing is self-reported, and payment cannot influence a shelf. That provenance/trust disclosure is helpful, though return format and pagination remain unstated.

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?

Purpose is front-loaded in the opening clause, and the three sentences are dense but each carries content. The shelf enumeration and the closing provenance sentence are somewhat flourishy, but nothing is pure padding. Reasonably sized for a two-mode lookup.

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, zero-required-param lookup with annotations covering the safety profile, the description conveys the two operational modes and the trust model behind the data. With no output schema, it does not describe row fields or result shape, but that gap is minor given the annotations and 100% schema coverage.

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%, so both parameters are already documented (shelf filter values and 'omit domain for corpus-wide counts'). The description's prose enumeration of shelves loosely parallels the schema's enum list but adds no syntax or format detail beyond what the schema provides. 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+resource: checks registry membership for a domain and enumerates what it serves (llms.txt, agents.md, media kit, entity graph, AI access policy, agent-callable surfaces). It also notes the no-domain mode returns corpus-wide shelf counts. However, it never distinguishes itself from plausible siblings like corpus_state, public_counts, or machine_record, leaving the agent to guess which registry tool to pick.

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 only usage guidance is that omitting domain yields corpus-wide shelf counts, which is more of a parameter behavior than a when-to-use statement. There is no explicit 'use this instead of X' routing and no stated exclusions against the many sibling tools. Usage is implied rather than prescribed.

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