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

Annotations already declare readOnly=true, destructive=false, openWorld=false, so the safety profile is covered; the description still adds real value beyond that by explaining the output shape (one card per line, grouped by who made it, with counts and where the owner answers) and by giving an explicit null-handling rule: report null tokens as 'no recorded cost' and 'never a guess'. It says nothing about volume limits or pagination, and the 'whatEachCost' clause is attached without explanation of where that data comes from relative to the schema.

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?

The purpose and the sibling routing are front-loaded and the two negative pointers are stated compactly in a single line each. The final 'whatEachCost' sentence is a run-on that packs token-ledger provenance, null semantics and an instruction to the agent into one dense clause, costing readability, though every sentence does carry content.

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 zero-required-parameter, read-only listing tool with no output schema, the description covers what is returned, how it is grouped, how it differs from the two nearest alternatives, and how to interpret the cost figures. The only real gap is that 'whatEachCost' is introduced as if it were a callable option while the schema exposes only 'project', leaving the agent unsure whether it is an output field or an argument.

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% on the single optional 'project' parameter, so the schema already carries the semantics of 'id or exact name, optional when the account has one project'. The description does not mention the project parameter at all, adding no meaning beyond the schema, which is the baseline 3 case.

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 — 'Lists every card that waits for the owner' — and explicitly demarcates scope against card_read and freezer_read, so an agent can distinguish it from siblings. The trailing 'whatEachCost' passage blurs the picture, since it reads like a parameter or output field that does not exist in the schema, but the core purpose statement is still clear and front-loaded.

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 explicit routing rules: a card's own words/content/history belong to card_read, and cards whose moment passed belong to freezer_read, 'not here'. That is genuine when-not-to-use guidance. It never states the positive condition ('use this when the owner needs to see outstanding waiting cards'), which is implied rather than spelled out, so it falls short of a full 5.

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