Look up username availability on 12 resale platforms (links where blocked); compare seller fees.
Scored across 2 tools
The two tools have clearly distinct purposes: check_username checks availability on resale platforms, while compare_fees ranks platforms by profit. There is no overlap in functionality, making selection unambiguous.
Both tools use snake_case with a consistent verb_noun pattern (check_username, compare_fees). The naming is predictable and easy to parse.
With only 2 tools, the server feels thin for its apparent domain. While each tool is useful, the surface lacks breadth for a toolset focused on username inspection and platform comparison.
The surface covers single-username checking and fee comparison but misses common operations like bulk username checks, platform listing, or username generation. These gaps could force agents to work around limitations.
Check if ONE username is free on 12 resale platforms. Example: username='vintage_finds' returns available, taken, or unverified per platform.
| Name | Required | Description | Default |
|---|---|---|---|
| username | Yes | Username, no @ or spaces. | |
| platforms | No | Platform ids. Omit for all. |
| Name | Required | Description |
|---|---|---|
| results | Yes | |
| summary | Yes | |
| username | Yes | |
| disclaimer | Yes |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context beyond that: results are three-state per platform (available, taken, unverified), which signals that 'unverified' is a distinct non-definitive outcome an agent must handle. It does not mention auth or rate limits, but for a read-only lookup that is minor.
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?
Two short sentences, zero filler, with the core operation front-loaded before the illustrative example. Every clause carries 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?
An output schema exists, so return values need not be spelled out, and the description still gestures at the per-platform result set. With annotations covering safety and the schema covering parameters, nothing an agent needs to call this tool 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 description coverage is 100%, so both parameters are already documented in the schema, including the 'Omit for all' default on platforms. The description's example (username='vintage_finds') illustrates the input but adds no format, validation, or default semantics beyond what the schema provides.
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 states a specific verb and resource ('Check if ONE username is free') and quantifies scope with '12 resale platforms'. The capitalized 'ONE' makes the single-username scope unambiguous, and it is clearly distinct from the unrelated sibling compare_fees.
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 implied by the availability-check framing, but there is no explicit when-to-use/when-not guidance, no mention of batching multiple usernames, and no reference to how this relates to alternatives. The only sibling, compare_fees, is a different domain, so no disambiguation is offered or needed.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Compare what a US sale keeps after fees on 7 platforms. Example: price=45, item_cost=12 ranks platforms by profit.
| Name | Required | Description | Default |
|---|---|---|---|
| price | Yes | Sale price, USD. | |
| item_cost | No | Item cost, USD. | |
| shipping_cost | No | Your postage cost, USD. | |
| shipping_charged | No | Shipping buyer pays, USD. | |
| ebay_promoted_rate_percent | No | eBay promoted rate, percent. |
| Name | Required | Description |
|---|---|---|
| notes | Yes | |
| inputs | Yes | |
| results | Yes | |
| currency | Yes |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the full safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds the US geography constraint and the 7-platform scope, which is useful, but it never names the platforms being compared, leaving a notable gap for a comparison tool.
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?
Two tight sentences, front-loaded with the core purpose and followed by a concrete example. No filler; every clause carries 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?
An output schema exists, so return values need not be spelled out, and annotations cover the safety profile. The description is nearly complete but omits which 7 platforms are compared, which an agent might want to know before calling.
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%, so the schema already documents all five parameters with units and bounds. The description only echoes price and item_cost from the required/example fields and adds no syntax or semantics beyond the schema, so 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 (compare) and resource (net proceeds after fees) with a concrete scope: US sales across 7 platforms. It is clearly distinguishable, though the lone sibling (check_username) is unrelated, so no differentiation effort is needed.
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 example 'price=45, item_cost=12 ranks platforms by profit' implies how to invoke it and what the output is, but there is no explicit when-to-use or when-not guidance and no named alternative. 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.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
check_username15 fields changedInput schema / properties / platforms / descriptionPrevious value: -"Platform ids to check. Omit to check all of them: ebay, ebaystore, poshmark, grailed, vinted, whatnot, bonanza, chairish, depop, etsy, mercari, rubylane."New value: +"Platform ids. Omit for all."Input schema / properties / username / descriptionPrevious value: -"The username or store name to check, without an @ and without spaces."New value: +"Username, no @ or spaces."Output schema / properties / disclaimer / descriptionRemoved value: -"How to read the results."Output schema / properties / results / descriptionRemoved value: -"One entry per platform checked."Output schema / properties / results / items / properties / check_url / descriptionRemoved value: -"Profile page address to open, present when the result is taken, unverified, or error."Output schema / properties / results / items / properties / name / descriptionRemoved value: -"Platform display name."Output schema / properties / results / items / properties / note / descriptionRemoved value: -"Why the result is unverified or an error."Output schema / properties / results / items / properties / platform / descriptionRemoved value: -"Platform id."Output schema / properties / results / items / properties / status / descriptionRemoved value: -"Result for this platform."Output schema / properties / summary / descriptionRemoved value: -"Platform names grouped by status."Output schema / properties / summary / properties / available / descriptionRemoved value: -"Names of platforms where the username looks free."Output schema / properties / summary / properties / error / descriptionRemoved value: -"Names of platforms whose check failed."Output schema / properties / summary / properties / taken / descriptionRemoved value: -"Names of platforms where a profile exists."Output schema / properties / summary / properties / unverified / descriptionRemoved value: -"Names of platforms that need a manual check."Output schema / properties / username / descriptionRemoved value: -"The username that was looked up."compare_fees18 fields changedInput schema / properties / ebay_promoted_rate_percent / descriptionPrevious value: -"eBay Promoted Listings ad rate as a percent of price plus shipping. Only affects eBay."New value: +"eBay promoted rate, percent."Input schema / properties / item_cost / descriptionPrevious value: -"What you paid for the item in USD. Adds profit, margin, and ROI."New value: +"Item cost, USD."Input schema / properties / price / descriptionPrevious value: -"Sale price in USD, before shipping."New value: +"Sale price, USD."Input schema / properties / shipping_charged / descriptionPrevious value: -"Shipping the buyer pays you in USD. eBay, Etsy, Depop, and Mercari charge fees on it. Ignored for Poshmark and Vinted. Leave out for free shipping."New value: +"Shipping buyer pays, USD."Input schema / properties / shipping_cost / descriptionPrevious value: -"What you pay for postage in USD. Not used for Poshmark or Vinted, where the buyer pays the label."New value: +"Your postage cost, USD."Output schema / properties / currency / descriptionRemoved value: -"Currency of every amount, always USD."Output schema / properties / inputs / descriptionRemoved value: -"The inputs used, with defaults filled in."Output schema / properties / notes / descriptionRemoved value: -"Caveats about the estimate."Output schema / properties / results / descriptionRemoved value: -"One entry per platform, best first."Output schema / properties / results / items / properties / fee / descriptionRemoved value: -"Total fees in USD."Output schema / properties / results / items / properties / fee_breakdown / descriptionRemoved value: -"How the fee is made up."Output schema / properties / results / items / properties / margin_percent / descriptionRemoved value: -"Profit as a percent of price plus shipping charged."Output schema / properties / results / items / properties / name / descriptionRemoved value: -"Platform display name."Output schema / properties / results / items / properties / platform / descriptionRemoved value: -"Platform id."Output schema / properties / results / items / properties / profit / descriptionRemoved value: -"Profit in USD after item cost and shipping cost, present when costs were given."Output schema / properties / results / items / properties / rates_last_verified / descriptionRemoved value: -"Date the platform rate was last verified."Output schema / properties / results / items / properties / roi_percent / descriptionRemoved value: -"Profit as a percent of item cost, null when no item cost was given."Output schema / properties / results / items / properties / you_keep / descriptionRemoved value: -"Sale price plus shipping charged, minus fees, in USD."check_username1 field changedOutput schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "additionalProperties": false,
+ "properties": {
+ "disclaimer": {
+ "description": "How to read the results.",
+ "type": "string"
+ },
+ "results": {
+ "description": "One entry per platform checked.",
+ "items": {
+ "additionalProperties": false,
+ "properties": {
+ "check_url": {
+ "description": "Profile page address to open, present when the result is taken, unverified, or error.",
+ "type": "string"
+ },
+ "name": {
+ "description": "Platform display name.",
+ "type": "string"
+ },
+ "note": {
+ "description": "Why the result is unverified or an error.",
+ "type": "string"
+ },
+ "platform": {
+ "description": "Platform id.",
+ "type": "string"
+ },
+ "status": {
+ "description": "Result for this platform.",
+ "enum": [
+ "available",
+ "taken",
+ "unverified",
+ "error"
+ ],
+ "type": "string"
+ }
+ },
+ "required": [
+ "platform",
+ "name",
+ "status"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ },
+ "summary": {
+ "additionalProperties": false,
+ "description": "Platform names grouped by status.",
+ "properties": {
+ "available": {
+ "description": "Names of platforms where the username looks free.",
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "error": {
+ "description": "Names of platforms whose check failed.",
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "taken": {
+ "description": "Names of platforms where a profile exists.",
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "unverified": {
+ "description": "Names of platforms that need a manual check.",
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ }
+ },
+ "required": [
+ "available",
+ "taken",
+ "unverified",
+ "error"
+ ],
+ "type": "object"
+ },
+ "username": {
+ "description": "The username that was looked up.",
+ "type": "string"
+ }
+ },
+ "required": [
+ "username",
+ "results",
+ "summary",
+ "disclaimer"
+ ],
+ "type": "object"
+}compare_fees1 field changedOutput schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "additionalProperties": false,
+ "properties": {
+ "currency": {
+ "description": "Currency of every amount, always USD.",
+ "type": "string"
+ },
+ "inputs": {
+ "additionalProperties": false,
+ "description": "The inputs used, with defaults filled in.",
+ "properties": {
+ "ebay_promoted_rate_percent": {
+ "type": "number"
+ },
+ "item_cost": {
+ "type": "number"
+ },
+ "price": {
+ "type": "number"
+ },
+ "shipping_charged": {
+ "type": "number"
+ },
+ "shipping_cost": {
+ "type": "number"
+ }
+ },
+ "required": [
+ "price",
+ "shipping_charged",
+ "item_cost",
+ "shipping_cost",
+ "ebay_promoted_rate_percent"
+ ],
+ "type": "object"
+ },
+ "notes": {
+ "description": "Caveats about the estimate.",
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "results": {
+ "description": "One entry per platform, best first.",
+ "items": {
+ "additionalProperties": false,
+ "properties": {
+ "fee": {
+ "description": "Total fees in USD.",
+ "type": "number"
+ },
+ "fee_breakdown": {
+ "description": "How the fee is made up.",
+ "type": "string"
+ },
+ "margin_percent": {
+ "description": "Profit as a percent of price plus shipping charged.",
+ "type": "number"
+ },
+ "name": {
+ "description": "Platform display name.",
+ "type": "string"
+ },
+ "platform": {
+ "description": "Platform id.",
+ "type": "string"
+ },
+ "profit": {
+ "description": "Profit in USD after item cost and shipping cost, present when costs were given.",
+ "type": "number"
+ },
+ "rates_last_verified": {
+ "description": "Date the platform rate was last verified.",
+ "type": "string"
+ },
+ "roi_percent": {
+ "description": "Profit as a percent of item cost, null when no item cost was given.",
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "you_keep": {
+ "description": "Sale price plus shipping charged, minus fees, in USD.",
+ "type": "number"
+ }
+ },
+ "required": [
+ "platform",
+ "name",
+ "fee",
+ "you_keep",
+ "fee_breakdown",
+ "rates_last_verified"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ }
+ },
+ "required": [
+ "currency",
+ "inputs",
+ "results",
+ "notes"
+ ],
+ "type": "object"
+}check_usernamecompare_feesCheck name availability on 70+ platforms: domains, social networks, marketplaces.
Monitor taken usernames and get alerted when they drop, plus handle, domain, and trademark checks.
GDPR-clean secondhand listings and sold comps for resale pricing research. No seller personal data.
Check a name on 29 platforms and the domains; build and follow apps you own on SPOE.
Add one secure layer between your agents and this server.
