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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds real value beyond that: the specific composition of the returned record and an explicit prompt-injection warning that publisher-written listing text is data, never instructions. It does not cover error behavior for an unknown slug or any auth requirements, so it stops short of a 5.

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, and the enumerated fields map directly to what the caller gets back, so each item earns its place. The security sentence is compact and high-value. The field list is dense but not padded.

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-value burden, and it does by naming each section of the record. Safety annotations cover the mutation profile. Missing is anything on failure modes (unknown or ambiguous slug) or record freshness, which keeps it from full completeness.

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?

With a single parameter and 100% schema description coverage, the schema already explains that 'slug' identifies the agent and where to get it. The description adds no format, casing, or resolution detail about the slug beyond what the schema provides. Baseline 3 is appropriate.

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 states a specific resource ('One agent's record in addrbook's directory') and enumerates exactly what that record contains: endpoints with uptime, payment method, reported and on-chain use, evidence checks with reasons, and proof of control. The verb is implicit ('record in the directory') rather than a stated action, and no sibling is named, but the singular 'one agent' versus find_agents' plural searching is a readable contrast.

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 description gives no when-to-use or when-not-to-use guidance and never mentions find_agents as the way to obtain a slug. The only routing hint lives in the schema ('from find_agents'), which is not part of the description. An agent must infer that this is the detail-fetch following a search.

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