Get one resource record

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

The annotations already declare readOnlyHint=true and openWorldHint=true, so the description doesn't need to restate safety. It adds significant behavioral value by explaining how the summary mode transforms bulky fields into size stats, including a concrete example (block drops ~2,750 → ~150 tokens). This goes beyond the schema by revealing the token-cost impact, which is not visible from the annotations or schema. The description doesn't contradict annotations.

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 concise, well-structured, and front-loaded with the core purpose. The token-cost guidance is placed after the main action, making it easy to scan. Every sentence adds value, with no redundant filler. The example of token reduction is a high-impact detail delivered efficiently.

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 read-only fetch tool with 4 parameters, the description covers the key decision points: how to control token cost via summary and fields, and the id vs name distinction for tags. The output schema is absent, so the description should clarify what the return value looks like; it does partially by describing summary and fields outputs. However, it doesn't mention error cases or how to know which resource types support name-based lookup, but given the complexity and the schema's completeness, this is adequate.

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 schema's description coverage is 100%, so every parameter is documented there. The description adds some extra meaning by explaining how 'fields' and 'summary' interact (e.g., fields returns only top-level fields plus id, summary returns overview with size stats). However, it doesn't fully clarify the relationship between summary and fields (e.g., can they be combined?), which is a limitation. Still, given high schema coverage, a baseline of 3 is appropriate, with modest increments from the added context.

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 verb ('Fetch'), a resource ('a single record of a resource'), and identifies the key identifier ('by its id'). It also notes the special case for tags (name instead of id), which adds clarity. This clearly distinguishes it from sibling tools like list_resource and find_resource.

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 explicitly explains when to use the summary and fields options to control token cost, and implicitly guides the choice between the full record versus cheaper variants. It contrasts with potential alternatives by focusing on fetching a single record versus listing or finding, though it doesn't explicitly name alternative tools. However, the guidance on option selection is strong, and the context is clear enough.

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