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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered. The description adds the scope of the returned record (stats, traits, skills, locations, provenance), which is useful. It doesn't mention error behavior for invalid IDs, but with annotations covering the safety profile, a 3 is appropriate.

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?

One sentence, front-loaded with the resource and fields, zero waste. Every word 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?

For a simple read-by-ID tool with two required params and full annotation coverage, the description is nearly complete. The only gap is that the chronicle parameter is not explained in the description, though the schema enum makes it self-documenting. No output schema exists, but the description lists the returned categories, which is sufficient.

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 0%, so the description must compensate. It explains that npcId is a numeric NPC ID and that the record includes stats/traits/etc., but it doesn't explain the chronicle parameter at all. The schema's enum and required fields carry the rest, so the description adds partial but not complete meaning.

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 uses a specific verb ('Get') and names the resource ('NPC record') plus the exact fields returned ('stats, traits, skills, locations and provenance'). It also specifies the ID type ('numeric NPC ID'), which distinguishes it from sibling search_npcs and get_npc_drops.

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 implies this is the direct fetch-by-ID tool, and the sibling list includes search_npcs for finding IDs and get_npc_drops for a different resource. It doesn't explicitly state 'use search_npcs when you don't have an ID', but the contrast is clear enough.

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