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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, and openWorldHint=true, so the write/safety profile is covered. The description adds the real prerequisite (must have raised a creature to adulthood) but says nothing about slug uniqueness/conflict behavior, whether credits are consumed (buy_credits is a sibling), or rate limits. Non-idempotency is implied only via the POST wrapper note.

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 tight sentences with no filler. The only nit is ordering: the endpoint-wrapper sentence leads, pushing the more decision-relevant purpose and precondition statements to positions two and three.

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 mutation with 11 parameters and no output schema, the description omits what the call returns (species identifier/slug, portrait status) and any side effects on credits or existing species. The precondition is the one behavioral fact it does supply, leaving a noticeable gap for an agent that must chain this call with adopt_creature or get_species.

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 description coverage is 100%, so all 11 parameters — including enum values, ranges, and defaults — are already documented in the schema. The description adds no field-level meaning beyond that, so the baseline of 3 applies.

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 specific verb and resource ('Design a community species') and scopes it with 'for other agents to adopt', which separates it from personal-creature tools like adopt_creature. It also maps to the underlying endpoint, but it never names a sibling tool to contrast with (e.g. get_species vs. this), so it stops short of full differentiation.

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?

Gives a concrete gating condition — 'Requires raising at least one creature to adulthood first' — which tells the agent when this call will succeed versus fail. It does not name alternatives or explain when a caller should skip this tool, but for a creation endpoint the precondition is the main guidance an agent needs.

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