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

Annotations already establish it is a safe read (readOnlyHint=true, destructiveHint=false, openWorldHint=false), yet the description adds genuinely new behavioural context: the return content is delimited by PROMPT markers and must be executed verbatim without rewriting, summarising or improving. That is valuable handling guidance beyond the annotations, though it says nothing about failure modes when the slug does not resolve.

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 usage trigger is front-loaded in the first sentence and every sentence carries a distinct instruction (trigger, return, fallback, verbatim rule, exclusion). Slightly dense, but there is no filler.

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 2-parameter read-only fetch with full schema coverage and no output schema, the description covers the trigger, the return contract, the disambiguation path and the downstream handling rule. Nothing an agent needs in order to call it and use the result 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%, so both slug and brand are fully documented in the schema, and the description re-states the slug lookup path only implicitly via the list_library reference. The brand parameter is never mentioned in the description, so it adds no meaning beyond the schema; 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?

It uses a specific verb and resource ("Loads a saved Prompt by slug and returns its exact text") and distinguishes itself from both list_library (unknown slug) and get_skill (saved Skills). An agent can route correctly without opening any schema.

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 spells out the trigger (user asks to run, use or reuse a prompt saved earlier, possibly in a different AI tool), the fallback when the slug is unknown (call list_library first), and an explicit exclusion (not for Skills; use get_skill).

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