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

Annotations (readOnlyHint, idempotentHint, destructiveHint=false) already cover the safety profile. The description adds useful behavioral context: the tool returns documentation as markdown and enumerates the covered topics summarises the input schema's fallback behavior. No contradiction with annotations.

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?

One tightly-scoped sentence that is front-loaded ('Self-serve documentation') and groups related content with a dash. every phrase earns its place; no filler or repetition.

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?

Given a single optional parameter with full schema coverage, a read-only/idempotent annotation, and an output schema, the description covers the tool's scope and output format sufficiently. The fallback behavior for invalid topics is captured in the schema, completing the picture.

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% – single parameter `topic` with allowed values and fallback behavior fully described. The tool description only restates the topic areas already in the enum, adding no meaning beyond the schema.

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 the action (self-serve documentation), the resource (AgentLedger API), the topics covered, and the output format (markdown). This distinguishes it clearly from siblings like ledger_alerts or ledger_set_budget without needing to inspect their schemas.

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 description makes the usage context clear: fetch AgentLedger API docs. It doesn't explicitly name alternatives or exclusions (e.g., 'for alerts, use ledger_alerts'), but no sibling competes for this purpose, so an agent can infer when to use it. The `topic` parameter adds more granular guidance in the schema.

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