Fetch metrics for one specific Featured App by its app_id (contract id from the Scan API). Returns name, category, TVL, 24h volume, user count, and last activity from the Featured Apps registry. Canton-specific. TVL / volume / users may be null when only the Scan API source is available.
| Name | Required | Description | Default |
|---|---|---|---|
| app_id | Yes | Featured-app contract id, or a unique prefix of it as shown by list_featured_apps. |
Changes observed during successful MCP inspections.
Input schema / $schemaPrevious value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"Input schema / properties / app_id / descriptionPrevious value: -"Featured-app contract id (long hex string from list_featured_apps)."New value: +"Featured-app contract id, or a unique prefix of it as shown by list_featured_apps."Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower. The description still adds real value beyond them: it enumerates the returned fields and warns that TVL/volume/users may be null when only the Scan API source is available, which prevents an agent from treating nulls as an error.
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?
Four short sentences, front-loaded with the action and scope, then the return payload and the null caveat. No filler, though the return-field list could be tightened.
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, so the explicit enumeration of returned fields plus the null-source caveat is exactly the compensation needed. What remains uncovered is minor: error behavior for an unknown or ambiguous prefix.
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 schema already documents both the contract-id meaning and prefix support. The description's '(contract id from the Scan API)' largely restates the schema, so it adds only marginal meaning.
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 ('Fetch metrics for one specific Featured App by its app_id') and scopes it to a single app, which distinguishes it from the plural listing tool. It does not name list_featured_apps as the sibling that produces those ids in the description itself, keeping it short of a 5.
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 phrase 'one specific Featured App' implies you need an app_id in hand, and the schema points to list_featured_apps for discovery. However, there is no explicit when-to-use/when-not or named alternative in the description, so usage is only implied.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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