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. The description adds the useful default behavior (falls back to caller's user spend), but says nothing about aggregation granularity, time window, or whether scopes can be combined — notable gaps for a reporting tool with no output 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?

Two compact sentences, front-loaded with the purpose and then the scoping modes; no filler. It is arguably over-compressed, since the ambiguity around scope vs. user_id could have been resolved with one extra clause, 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?

No output schema exists, and the description does not need to describe return values in depth, but it also omits any hint of the shape of a 'rollup' or the time range covered. Combined with the missing user_id parameter referenced in the text, the definition is close to sufficient for a zero-required-param read tool but not fully self-consistent.

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?

With only 25% schema coverage, the description must carry the burden, and it does partially: it clarifies that repo scoping requires the owner+repo pair, which the flat schema does not convey. But it directs scoping via "user_id (self)", a parameter that does not exist in the schema (the schema uses scope='user'), and it never explains how the 'scope' param interacts with the other fields, leaving a genuine ambiguity.

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 opens with a specific verb and resource: "Return AI spend rollups," which tells an agent this is a read of aggregated cost data. It is reasonably distinguishable from cost-adjacent siblings like merjax_list_token_spend and merjax_get_agent_budget, though it never names those siblings to draw the line explicitly.

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?

It states the three scoping modes and the default (caller's user spend), which implies when each scoping choice applies. However, it gives no explicit when-to-use/when-not-to guidance and no pointer to the alternative cost tools (list_token_spend, get_agent_budget) that an agent could easily confuse with this one.

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