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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, but the description adds meaningful behavior beyond those: the idempotency caveat that the same slug returns the same entry until its health probe changes, the explicit error semantics (unknown/unapproved slug is an error, not empty), and the contents of the returned {entry} including the 6-hourly health probe. These details inform the agent's expectations without contradicting the structured hints.

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 description is longer than average but well-structured: purpose is front-loaded, followed by behavioral traits, return payload, and usage routing. Most sentences earn their place—particularly the routing instructions and error semantics—but the read-only/idempotent restatement slightly duplicates annotations. Minor redundancy prevents a 5.

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?

Given a single fully-documented parameter, a rich output schema, and strong annotations, the description adds the remaining context needed for correct invocation: error behavior, idempotency edge case (health probe changes), and explicit routing to alternatives. Nothing an agent needs to decide or call 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?

Schema coverage is 100% and the slug parameter is fully documented in the schema (lowercase, 1-80 chars, case-sensitive, example values, approved-only resolution). The description reinforces that the slug must be exact and already known, but it does not add semantic meaning beyond what the schema already provides. Baseline 3 is appropriate under high schema coverage.

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 opens with a specific verb and resource: 'Fetch the full record of ONE approved registry entry whose exact slug you already have.' It explicitly contrasts with sibling tools by noting the detail level the listing tools omit, and points to search_registry, discover_capabilities, and list_entries for other lookup modes. An agent can immediately tell this is the single-record keyed lookup.

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 guidance is explicit and actionable: use this tool when you already possess an exact slug (e.g., from a prior tool result); if you lack a slug, do not guess and instead use search_registry, discover_capabilities, or list_entries. It also states that the tool takes no filters and no paging, and that unknown/unapproved slugs produce an error. This is model how-to-use guidance with named alternatives and conditions.

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