get_sticker

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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint, so the 'Read-only' sentence is partly redundant, but the description earns its keep by disclosing the return payload ({base64}) and that the image format follows the sticker's contentType, usually image/webp. It does not discuss size limits or failure modes for missing sticker IDs.

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 sentences, front-loaded with the core action and result, then provenance, then the alternative tool. The '(required, hex string)' restatement and 'Read-only' repeat what the schema and annotations already carry, a small amount of waste.

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, yet the description compensates by naming the exact return shape and format, plus the ID sources. For a two-parameter read tool, an agent has everything needed to invoke it correctly.

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 the baseline is 3, but the description adds real provenance detail beyond the schema: pack_id is a hex string from list_sticker_packs' packId field, and sticker_id maps to stickers[].id. That helps an agent construct valid calls rather than guess.

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 and resource ('Fetch one sticker image from an installed pack') and even names the return encoding (base64). This clearly separates it from the sibling send_sticker / send_group_sticker tools that deliver rather than fetch.

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?

Explicitly routes the agent: 'Use send_sticker or send_group_sticker to send it instead of downloading it,' which is exactly the when-not guidance needed given the adjacent send tools. It also states where both IDs must come from (list_sticker_packs or add_sticker_pack).

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