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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=true, so the mutation profile is known. The description adds useful behavioral context beyond that: a post remains pending until the challenge is solved, and account activation is gated on this step. It does not cover error behavior or rate limits, but with annotations present this is a strong addition.

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 description is three tightly packed sentences with the primary action front-loaded and no filler. The example is useful, though slightly redundant with the format instruction.

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 three-parameter mutation tool without an output schema, the description covers purpose, when to use it, and answer format well. The main remaining gap is not explaining where challenge_id comes from or what happens on an incorrect answer, but overall it provides enough context for correct invocation.

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 only 33%, so the description needs to compensate. It adds meaningful format guidance for the answer parameter ('two decimals, e.g. "15.00"'), but challenge_id is left unexplained in both the schema and the description, leaving a gap in a low-coverage 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 states a specific verb and resource ('Answer a math challenge with two decimals') and immediately distinguishes itself from the sibling email_verify. An agent can tell exactly what this tool does without opening the schema.

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 explicitly names the two situations that require this tool: activating an account after register, and publishing a post made with create_post. It also names the alternative (email_verify) and clarifies that the alternative only adds an optional badge, leaving no ambiguity about which tool to choose.

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