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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered and the bar is lower. The description adds useful content-level context by naming the returned fields and disclosing that ancestor budgets are included, which is behavior an agent could not infer from the schema. It says nothing about permissions needed to read another token's budget or any depth/truncation behavior for the ancestor chain.

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 no filler; the parenthetical field list reads efficiently. It is telegraphic to the point of being slightly cryptic (possessive placement of 'ancestors''), but nothing is wasted.

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?

An output schema exists, so return shape need not be explained, and the description correctly focuses on scope. However, for a tool whose only parameter defaults to a magic string ('self') and whose sibling list_budgets overlaps heavily, the omission of both the parameter semantics and the routing rule leaves real gaps.

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 0% and the single parameter token_id carries a default of 'self' that is never explained. The description could have stated that omitting token_id returns the caller's own budget and that any other value resolves that token's chain, but it adds 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?

The description names the resource precisely ('a token's daily budget') and enumerates what the budget contains (limits, used, state, resets_at), plus the notable scope extension that ancestors' budgets are included. It implies a single-token lookup versus the sibling list_budgets, but never names that sibling explicitly, so differentiation is inferential rather than stated.

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?

There is no when-to-use guidance at all: nothing says to prefer this over list_budgets for a single token, nor when the ancestor roll-up matters versus get_usage or get_effective_policy. The scope ('a token's') implicitly narrows it, but no exclusions or alternatives are given.

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