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

Annotations already carry the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description adds value by disclosing the returned fields (location, adoption page, email, phone) and that the target may be either a rescue or a shelter — useful given there is no output schema. It omits error behavior for an unknown or mismatched id.

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?

A single front-loaded sentence with zero filler: entity, key, provenance, and payload are all packed in without redundancy.

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 one-parameter read tool with full annotations and no output schema, the description covers what it returns and where the id comes from, which is most of what an agent needs. Missing only edge-case behavior (invalid id, unknown entity type).

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 0%, so the description must compensate and it partially does by explaining that id comes from a pet's rescue.id and can denote a rescue org or a shelter. It does not explain the strict id prefixes encoded in the schema pattern (rg-org-, tw-shelter-, us-shelter-, etc.), leaving format detail undocumented in prose.

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 ('One rescue or shelter by id') and even names the id's origin ('from a pet's rescue.id'), which clearly separates it from get_pet and find_pets. It stops short of naming an alternative sibling, so it is clear rather than maximally differentiating.

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 parenthetical '(from a pet's rescue.id)' gives real, actionable context: the agent learns to source this id from a pet record, implying it is a secondary lookup after get_pet. There is no explicit when-not guidance or named alternative (e.g., resolve_place), so usage remains implied rather than stated.

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