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

Annotations already disclose that this is a non-readonly, non-destructive, non-idempotent mutation, so the description's added value is the effect profile: happiness increases, energy decreases, with per-species variation (Cheeky gains most, Curious learns a little). That is genuine behavioral context an agent cannot get from the annotations. It omits guardrails such as cooldowns, minimum energy, or what happens when energy is exhausted.

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?

Compact and front-loaded: name, WHEN clause, effect summary, then an invocation example. Every element earns its place, though the parenthetical is slightly terse/opaque about what 'learns a little' mechanically means.

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?

An output schema exists, so return values need not be explained, and the tool is a simple zero-required-parameter action. The description covers purpose, trigger, and stat effects adequately; only edge-case behavior (energy exhaustion, cooldowns, failure modes) is missing.

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 the single parameter (auth key) is documented in the schema, so the description carries little burden here. The 'pet_play {}' example usefully signals that no parameters are required, but nothing beyond that is added.

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?

States a concrete verb+resource ('play with your pet') and immediately characterizes the effect ('happiness up, energy down'), which lets an agent distinguish it from siblings like pet_feed, pet_rest, or pet_teach. It stops short of naming those siblings explicitly, so it is clear but not fully differentiated.

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:' line gives a usage trigger, but it is essentially circular — you play with your pet when you want to play with your pet — with the real signal being the stat deltas. No when-not conditions (e.g. insufficient energy, cooldown) and no named alternatives are provided.

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