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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds real value beyond that by stating the catalog is machine-readable and that entries include meanings and retry guidance, i.e., it discloses what the agent gets back and how to act on it.

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 tight sentences: the first defines the resource and its contents, the second gives the usage trigger. Front-loaded, no filler, every clause earns its place.

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?

With no output schema, no parameters, and safety already carried by annotations, the description still explains the return content (error codes with meanings and retry guidance) and when to call it. Nothing an agent needs in order 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 the baseline is 4; there is no parameter surface for the description to clarify or for the schema to omit. Nothing more is needed here.

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 (a catalog of every Epsilon API error code) and what it contains (meanings and retry guidance). No sibling tool does anything similar, so an agent can distinguish it instantly from check_order, get_quote, search_docs, etc.

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?

It gives an explicit trigger: consult it whenever another tool returns an error code you must interpret or decide whether to retry. That is clear when-to-use guidance; the only thing absent is a when-not-to-use clause, which is largely moot since no alternative error-lookup tool exists.

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