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

Beyond readOnlyHint=true, it discloses a conditional return shape: when the owner hid claims, only the claim count comes back, not which items were claimed. It also states the authentication requirement (private owner link containing /m/) and that the call is non-mutating, which is exactly the context annotations cannot express.

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 and tight throughout, with no filler sentences. The only near-waste is 'Does not change anything,' which restates readOnlyHint=true already visible in annotations.

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 single-parameter read tool with an output schema and full annotation coverage, this covers the trigger, the credential, the failure mode, and the one conditional return case. An agent has everything needed to call it correctly and interpret the hidden-claims result.

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 link format is already documented there, so the description adds limited syntax detail. It does, however, add the negative constraint that a shared link will fail, which meaningfully narrows what value is acceptable beyond the schema's string type.

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 plus the exact questions it answers: how the list is going, how many claims, and who is getting what. The scope is distinct from the create/update siblings, so an agent can route without opening 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?

Opens with a concrete trigger ('when the list owner asks how their gift list is going'), then names an explicit exclusion ('Does not work with the shared link') and the required credential ('private owner link'). Nothing about selection is left to inference.

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