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

This is the definition's strongest contribution: a tool named "show" would normally read as a pure lookup, yet the description discloses that it refreshes lazy decay and folds in real match history for evolution — explaining why readOnlyHint=false and idempotentHint=false are set. That side-effect disclosure is exactly the context an agent needs before calling it casually or repeatedly.

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?

Front-loaded with the trigger, then the return payload, then the sibling differentiation, then a call example — a good information order with no filler. It is telegraphic to the point of being slightly dense, but nothing is wasted.

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?

With an output schema present, the description needn't document return structure, and it still covers the one surprising behavior (state refresh) plus the sibling distinction. The only minor gap is that it never mentions the optional auth key in prose, relying entirely on the schema.

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?

There is a single optional parameter (key) with 100% schema description coverage, so the schema already carries the semantics. The description adds nothing about the key or auth handling beyond what the schema states, which is the baseline expectation when coverage is complete.

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?

"See your pet right now" gives a specific verb+resource, and the description enumerates exactly what comes back (needs, bond, knowledge, stage, trait, mood, presence line). It explicitly contrasts with pet_presence ("line only"), so an agent can separate the two without inspecting 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?

The "WHEN:" clause names a concrete trigger (you want a full snapshot of your pet now) and names the alternative tool with the condition that selects it. It stops short of explicit when-not guidance (e.g., don't use this to feed/play/clean, which are separate siblings), so it is clear context but not a full routing rule set.

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