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

Annotations declare readOnlyHint and idempotentHint, but the description adds valuable behavioral context: it discloses the free/keyless tier with a rate limit, explains that a paid key unlocks additional fields (in-the-money value, filing description, as-filed quantities), and notes the output matches free/paid company page blocks. This goes well beyond the structured annotations without contradicting them.

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?

Three dense sentences, each earning its place: scope and contents, free-tier limitations, and paid-tier additions. The core purpose is front-loaded, and the structure makes the free vs paid distinction easy to parse. No fluff or repetition.

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?

With a single parameter and no output schema, the description fully covers what the tool returns and under what conditions, including the data fields and the free/paid behavior differences. An agent has enough information to call it correctly and understand the response shape.

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 100% — the schema already explains 'one ASX ticker code, e.g. BHP' and 'one company per call — there is no batch form.' The description reinforces 'one ASX company' but adds no new parameter-level meaning beyond what the schema provides. 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?

The description clearly identifies the resource as 'the option and convertible register for one ASX company' and specifies the exact data fields returned (code, security kind, type, exercise price, expiry, quantity). This distinguishes it from sibling tools like get_cash_runway or get_dilution_snapshot, which cover entirely different financial instruments or metrics.

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?

The description clarifies free vs paid API key usage and rate limits (~20 calls/day), but does not explicitly state when to prefer this tool over siblings or provide exclusions. The differentiation from siblings is only implied by the resource type, not by direct comparison or conditions.

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