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

With no annotations, the description carries the full burden and does so well: it declares read-only, names the required Last Price credential, and warns that an unclaimed workspace with a self-registration sandbox key returns 403. It also fixes the default ordering, which affects how consumers read results.

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?

Two sentences, nothing wasted. The core action and result ordering come first, filtering and paging next, and prerequisite/auth caveats last, which is the right priority order.

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 read-only list tool with no output schema, the description supplies the return shape (purpose, amount, currency, owner) plus ordering, paging and auth prerequisites. An agent has everything needed to call it and interpret results without further probing.

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%, so every parameter is already documented in the input schema with types, formats and bounds. The description restates the filters and paging but adds no semantics beyond the schema (e.g., no timezone or inclusive/exclusive guidance for the date range), so the baseline 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 ('List the costs recorded in your workspace') and immediately characterizes the payload: purpose, amount, currency, owning agent or customer, ordered newest first. That is enough for an agent to distinguish it from record_cost, get_cost_analytics and list_usage_events.

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 concrete usage context: filter by customer_id and date range, page with limit and offset. It does not explicitly exclude alternatives or say when to prefer get_cost_analytics or list_usage_events, so it stops just short of the top score.

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