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

Annotations only say readOnlyHint=false and destructiveHint=false, so the description carries the real behavioral load and does so: plain server-side string concatenation, no AI call, no quota consumed, idempotent (no duplicate context). It also states what it will NOT do (rewrite/regenerate the prefix), which is the key risk an agent could otherwise get wrong.

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?

Three sentences, all load-bearing, with the core behavior front-loaded before the alternative-tool routing. The nested parentheticals (cost note, get_cost reference) make it dense to parse, but nothing is redundant.

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 two-parameter mutation tool with no output schema, the description covers what it does, what it costs, its idempotency guarantee, what it does not do, and which sibling to use instead. An agent has everything needed to select and invoke it correctly.

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% and both parameters already carry descriptions and constraints (maxLength 500, minLength 3), so the baseline is 3. The description adds meaning beyond the schema by explaining the idempotency semantics of the `context` argument — already-present content is not duplicated — which affects how an agent should call it.

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 names a specific verb and target ('Append context to a board's prompt_prefix_en') and explicitly contrasts itself with lab_restyle_location, which is the nearest sibling. An agent can distinguish the two without opening either 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 gives both the when-not and the alternative: for prefixes that are 'empty, too thin or a raw field dump' the agent is routed to lab_restyle_location, and it explicitly warns against 'recreating the board'. That is an explicit decision rule, not an implied one.

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