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

With annotations already declaring readOnlyHint=true and destructiveHint=false, the description reinforces the read-only nature and adds context: it does not add or remove reactions, requires an API key, returns counts per type, and clarifies that zero counts are valid (not errors). This goes beyond the annotations, though it doesn't cover all edge cases like error handling.

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 with three short paragraphs, each serving a purpose: definition, usage guidance, and behavioral clarity. It is front-loaded with the core purpose, but the third paragraph could be slightly more compact, hence a 4 rather than 5.

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?

Given the simple input (one parameter) and the existence of annotations, the description covers the key aspects: what it does, when to use it, its read-only nature, and output contents. It might mention error handling or response format in more detail, but for this complexity level, it is quite complete.

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 the parameter semantics are fully defined in the schema. The description only implies that the parameter is an article ID from article tools, but does not add meaningful new information beyond the schema, so the baseline of 3 is appropriate.

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 clearly states the tool reads reaction totals and the authenticated account's reactions on one article, distinguishing it from mutation tools like add_reaction and remove_reaction. The scope (one article at a time) and the verb 'read' are specific.

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 explicitly tells the agent to use this tool before add_reaction or remove_reaction to know the current state, and contrasts it with those tools. It also notes the single-article limitation, which helps decide when to use it versus other tools.

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