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

Annotations already declare destructiveHint=true and readOnlyHint=false, so safety is covered; the description adds the genuinely useful blast-radius detail that existing bookings retain the discount while new usage is blocked. It stops short of stating reversibility, idempotency, or behavior when the id is unknown.

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 sentence, front-loaded with the action and followed by the two facts that matter (new usage blocked, existing bookings unaffected). No filler.

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 single-parameter mutation with annotations covering safety and no output schema, the description supplies the key effect semantics. Missing only edge-case behavior (non-existent id, already-ended discount, permanence), which is minor at this complexity.

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% and the single 'id' parameter is documented in the schema ('Discount id, from list_discounts'). The description adds nothing about the parameter, so the baseline 3 applies.

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+resource ('End a discount') and immediately defines what ending means, so the agent can distinguish it from update_discount, create_discount, and list_discounts without opening a schema. The scope statement ('guests can no longer use it') pins down the operation precisely.

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?

Usage is only implied: the description makes clear this is the termination path rather than a modification, but it never says when to prefer it over update_discount or what preconditions (e.g. discount must exist / not already ended) apply. No alternatives are named.

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