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

Annotations only cover the safety profile (readOnly=false, idempotent=false, destructive=false); the description goes well beyond that by disclosing the two possible outcomes ('registered' vs 'waitlist'), the atomic backend capacity check, the fee recorded (amountCents) in the response, and that no wallet charge occurs on this call. This is exactly the extra behavioral context annotations cannot express.

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?

Front-loads the action, then the outcome/fee behavior, then parameter provenance, then the write warning - a logical order with no filler. Slightly dense at four sentences, but each carries distinct information.

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 mutating registration tool with 4 params, an output schema, and annotations, the description covers outcome states, capacity semantics, billing implications, ID sources, and a confirmation warning. Nothing an agent needs to invoke it correctly is missing.

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 3 is the baseline, but the description adds provenance for the two required parameters (program_id from list_school_programs, student_id from get_my_context), which is real meaning beyond the schema's 'must be your own student' note.

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 (registers) and resource (one of the caller's own students, for a school program), and scopes it with concrete program categories (before/after-school care, enrichment, camp). An agent can distinguish this from the adjacent register_for_event without opening either 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?

Gives clear context: it names where each ID comes from (list_school_programs, get_my_context) and warns 'WRITE - confirm the student and program before calling.' It does not explicitly contrast with the sibling register_for_event, but the resource distinction makes routing unambiguous.

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